WO2024090544A1

WO2024090544A1 - Methacrylate-containing composition, method for producing methacrylic ester, polymerizable composition, and method for producing methacrylic acid polymer

Info

Publication number: WO2024090544A1
Application number: PCT/JP2023/038845
Authority: WO
Inventors: 達也鈴木; 悠栗原; 裕樹加藤; 紘一兼森; 航鳴好
Original assignee: 三菱ケミカル株式会社
Priority date: 2022-10-28
Filing date: 2023-10-27
Publication date: 2024-05-02

Abstract

The purpose of the present invention is to provide a methacrylate–containing composition that has high quality stability during storage.　The methacrylate-containing composition according to one example contains methacrylate, a compound (component A1) represented by formula (11), and a polymerization inhibitor (component B), wherein the concentration of the methacrylate is 98.00-99.99 mass%. R^1a, R^2a, R^3a, R^4a, R^5a and R^6a are: a monovalent group comprising a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, and a carbonyl group; an alkylthio group; or an arylthio group.　At least two among R^1a, R^2a, R^3a, R^4a and R^5a are a group other than a hydrogen atom.　R^7a is: a monovalent group comprising a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, and a carbonyl group; an alkylthio group; or an arylthio group.

Description

Methacrylic acid-containing composition, method for producing methacrylic acid ester, polymerizable composition, and method for producing methacrylic acid polymer

The present invention relates to a methacrylic acid-containing composition, a method for producing a methacrylic acid ester, a polymerizable composition, and a method for producing a methacrylic acid polymer.
This application claims priority based on Japanese Patent Application Nos. 2022-172927, 2022-172928, 2022-173123, 2022-173124, 2022-173222, and 2022-173223, all of which were filed with the Japan Patent Office on October 28, 2022. The contents of which are incorporated herein by reference.

Methacrylic acid (hereinafter also referred to as "MAA") is known to be an extremely useful substance used as an industrially important methacrylic acid ester and as a raw material for various types of polymers. For example, polymethyl methacrylate, a homopolymer of methyl methacrylate, is used in signboards, lighting equipment, automobile parts, building-related materials, light guide plates for flat displays, light diffusion plates, etc., taking advantage of its excellent transparency and weather resistance. Copolymers of methacrylic acid and other monomers are used in paints, adhesives, fiber treatment agents, resin modifiers, rubber modifiers, leather treatment agents, paper processing agents, lubricating oil additives, cement admixtures, concrete admixtures, latex, photosensitive resins, ion exchange resins, water treatment polymers, etc. Various methods for industrially producing methacrylic acid have been developed, and it is produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method (Non-Patent Document 1). In these manufacturing methods, purification such as distillation and crystallization is performed to remove unreacted raw materials and by-products contained in the produced methacrylic acid, resulting in methacrylic acid of a quality suitable for the intended use.

Methacrylic acid has a tendency to polymerize easily, so it is known that a polymerization inhibitor is added during the production of methacrylic acid and during storage of the produced methacrylic acid to maintain the quality of the methacrylic acid (Non-Patent Document 2). For example, Patent Document 1 describes that, among various polymerization inhibitors, methyl ether of hydroquinone (MEHQ) is particularly preferable. Patent Document 2 describes the addition of phenothiazine and hydroquinone as polymerization inhibitors to a methacrylic acid-containing material. Patent Document 3 describes the distillation of methacrylic acid in the presence of 4-methoxyphenol, which is a polymerization inhibitor. Patent Document 4 describes the use of a diphenylamine derivative as a polymerization inhibitor. Patent Document 5 describes the use of a benzenetriamine derivative as a polymerization inhibitor.

JP 2004-155757 A JP 2001-072639 A JP 2008-101013 A JP 2002-533309 A JP 2002-513034 A

However, even when the polymerization inhibitor is added, the quality of methacrylic acid may deteriorate during storage. Therefore, the present invention provides a methacrylic acid-containing composition that has high quality stability during storage.

The present inventors have conducted intensive research to achieve the above object. As a result, they have discovered that the inclusion of a compound with a specific structure in a methacrylic acid-containing composition improves the quality stability during storage and inhibits the decomposition of the polymerization inhibitor, thus completing the present invention.

According to one aspect of the present invention, the following methacrylic acid-containing composition is provided.
Methacrylic acid,
at least one selected from the group consisting of component A1 which is a compound represented by formula (11) below, component A21 which is a compound represented by formula (21) below, component A3 which is a compound represented by formula (31) below, component A4 which is a compound represented by formula (41) below, component A5 which is a compound represented by formula (51) below, and component A6 which is a compound represented by formula (61) below;
Contains
Furthermore, it optionally contains component B, which is a polymerization inhibitor, as necessary,
A methacrylic acid-containing composition having a concentration of methacrylic acid of 98.00 to 99.99% by mass.

In formula (11),
R ^1a , R ^2a , R ^3a , R ^4a , R ^5a , and R ^6a each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group, or an arylthio group;
two or more of R ^1a , R ^2a , R ^3a , R ^4a and R ^5a are groups other than a hydrogen atom;
R ^7a represents a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group, or an arylthio group.

In formula (21),
R ^1b , R ^2b , R ^3b and R ^4b each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group or an arylthio group.

In formula (31),
^R1c , ^R2c , ^R3c , ^R4c , ^R5c , ^R6c , and ^R7c each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group, or an arylthio group.

In formula (41),
^Rd represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 1 to 12 carbon atoms, and these groups may further have a substituent.

In formula (51),
R ^1e and R ^2e each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an alkylthio group, or an arylthio group;
R ^3e represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, an alkylthio group, or an arylthio group;
R ^1e and R ^2e , R ^2e and R ^3e , and R ^3e and R ^1e may be linked to each other to form a ring.
However, the total number of carbon atoms of R ^1e and R ^2e is 2 or more.

In formula (61),
R ^1f , R ^2f and R ^3f each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, an alkylthio group or an arylthio group;
R ^4f represents a monovalent group including an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group or a carbonyl group, an alkylthio group or an arylthio group.
However, this does not include the case where R ^1f = H, R ^2f = H, R ^3f = _CH3 , and R ^4f = OH, i.e., the case where the component A6 is methacrylic acid. The total number of carbon atoms of R ^1f , R ^2f , and R ^3f is 1 or more. H represents a hydrogen atom, C represents a carbon atom, and O represents an oxygen atom.

According to yet another aspect of the present invention, there is provided a method for producing a methacrylic acid ester, comprising esterifying the methacrylic acid in the methacrylic acid-containing composition.

According to yet another aspect of the present invention, a polymerizable composition is provided that contains the methacrylic acid-containing composition.

According to yet another aspect of the present invention, there is provided a method for producing a methacrylic acid polymer, which comprises polymerizing the polymerizable composition.

The present invention provides a methacrylic acid-containing composition with high quality stability in which decomposition of the polymerization inhibitor during storage is suppressed.

Several embodiments will be described below, but the present invention is not limited to the following.
In this specification, a numerical range expressed using "to" means a range including the numerical values before and after "to" as the lower and upper limits, and "A to B" means A or more and B or less. The lower and upper limits of the numerical ranges disclosed in this specification can be arbitrarily combined to form a new numerical range.

[Methacrylic acid-containing composition according to the first aspect]
The methacrylic acid-containing composition according to the first embodiment contains methacrylic acid, a component A1 which is a compound represented by the following formula (11), and a polymerization inhibitor, a component B. The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In formula (11), R ^1a , R ^2a , R ^3a , R ^4a , R ^5a and R ^6a each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group, and two or more of R ^1a , R ^2a , R ^3a , R ^4a and R ^5a are groups other than a hydrogen atom. R ^7a represents a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group.
In addition, the methacrylic acid-containing composition may contain other compounds (component C) and water as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the first aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A1)
The methacrylic acid-containing composition according to the first embodiment contains component A1, which is a compound represented by the formula (11). The coexistence of component A1 and component B described later can suppress the decomposition of the polymerization inhibitor during storage of the methacrylic acid-containing composition. The reason for this is presumed to be as follows.

Methacrylic acid is known to polymerize due to radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes into other compounds when trapping radicals, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated when oxygen molecules absorb ultraviolet light derived from sunlight. Component A1 is a π-conjugated compound having a benzene ring, so it absorbs ultraviolet light, and the absorption wavelength and absorption intensity change depending on the type of substituent. Component A1 has an alkyl group with appropriate bulkiness and appropriate electron donating property bonded to the benzene ring, so it can absorb ultraviolet light of a wide range of wavelengths. Therefore, when a methacrylic acid-containing composition contains component A1, ultraviolet light of a wide range of wavelengths is absorbed, and the generation of hydroxyl radicals is suppressed. This reduces the number of radicals that component B needs to trap, suppressing the decrease in the concentration of component B and the generation of decomposition products.

The molecular weight of component A1 is preferably 2000 or less. By having a molecular weight of 2000 or less, the number of benzene rings per unit mass in component A1 can be increased, so that the effects of the present invention can be obtained with a small mass. The molecular weight of component A1 is more preferably 1600 or less, even more preferably 1200 or less, and particularly preferably 800 or less.

R ^1a , R ^2a , R ^3a , R ^4a , R ^5a and R ^6a in the formula (11) each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^7a in the formula (11) represents a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group, and two or more of R ^1a , R ^2a , R ^3a , R ^4a and R ^5a are groups other than a hydrogen atom. R ^7a represents a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^1a , R ^2a , R ^3a , R ^4a , R ^5a , R ^6a and R ^7a may be the same or different.

In the formula (11), if the steric hindrance of R ^1a , R ^2a , R ^3a , R ^4a , R ^5a , R ^6a , and R ^7a is large, distortion occurs in the benzene ring and the π-conjugated system is not maintained. However, if R ^1a , R ^2a , R ^3a , R ^4a , R ^5a , R ^6a , and R ^7a satisfy the above conditions, the bulkiness is appropriately large and the π-conjugated system of component A1 is maintained, so that the compound has the property of absorbing ultraviolet light over a wide wavelength range and can obtain the effects of the present invention. From the viewpoint of increasing the absorbance of ultraviolet light and suppressing the generation of hydroxy radicals, R ^1a , R ^2a , R ^3a , R ^4a , R ^5a , and R ^6a are preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a hydroxy group, an alkoxycarbonyl group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxy group, or an alkoxycarbonyl group having 1 to 6 carbon atoms, further preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an i-butyl group, a hydroxy group, or a methoxy group, and particularly preferably a hydrogen atom, a hydroxy group, or a methoxy group. From the viewpoint of increasing the absorbance of ultraviolet light and suppressing the generation of hydroxy radicals, R ^7a is preferably a hydrogen atom, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, an alkoxycarbonyl group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, a carboxy group, or an alkoxycarbonyl group having 2 to 6 carbon atoms, and even more preferably a hydrogen atom, a carboxy group, or a methoxycarbonyl group.

The alkyl group is a chain (straight-chain or branched) alkyl group or a cyclic alkyl group. An alkyl group having 1 to 20 carbon atoms is preferred, an alkyl group having 1 to 10 carbon atoms is more preferred, and an alkyl group having 1 to 5 carbon atoms is even more preferred. Examples of chain alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, hexyl, octyl, decyl, hydroxymethyl, 1-hydroxyethyl, and 2-hydroxyethyl groups, with methyl, ethyl, n-propyl, isopropyl, and t-butyl groups being preferred. Examples of cyclic alkyl groups include cyclopentyl, cyclohexyl, and cyclooctyl groups.

The alkenyl group is a chain (straight-chain or branched) alkenyl group or a cyclic alkenyl group. An alkenyl group having 2 to 20 carbon atoms is preferred, an alkenyl group having 2 to 10 carbon atoms is more preferred, and an alkenyl group having 2 to 5 carbon atoms is even more preferred. Examples of chain alkenyl groups include vinyl groups, 1-propenyl groups, isopropenyl groups, 2-butenyl groups, 1,3-butadienyl groups, 2-pentenyl groups, and 2-hexenyl groups. Examples of cyclic alkenyl groups include cyclopentenyl groups and cyclohexenyl groups.

The aryl group is preferably an aryl group having 1 to 20 carbon atoms, more preferably an aryl group having 1 to 12 carbon atoms. Aryl groups include heteroaryl groups containing oxygen, nitrogen, sulfur, etc. Examples of aryl groups include phenyl, mesityl, naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, isoxazolyl, isothiazolyl, imidazolyl, oxazolyl, thiazolyl, thiadiazolyl, thienyl, triazolyl, tetrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrazolyl, pyrrolyl, furyl, furazanyl, isoquinolyl, isoindolyl, indolyl, quinolyl, pyridothiazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzotriazolyl, benzofuranyl, imidazopyridinyl, triazopyridinyl, and purinyl groups.

The alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably an alkoxy group having 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, n-pentoxy, isopentoxy, and phenoxy groups.

The amino group includes an amino group (-NH ₂ ) (0 carbon atoms) having no substituent on the nitrogen atom, and an amino group in which some or all of the hydrogen atoms bonded to the nitrogen atom have been replaced with carbon atoms. The number of carbon atoms in an amino group in which some or all of the hydrogen atoms bonded to the nitrogen atom have been replaced with carbon atoms is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6. Examples of the amino group include an amino group (-NH ₂ ) having no substituent, a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a dimethylamino group, a diethylamino group, an anilino group, a toluidino group, an anisidino group, a diphenylamino group, and an N-methyl-N-phenylamino group.

Examples of monovalent groups containing a carbonyl group include formyl groups, acyl groups, carboxy groups, amide groups, alkoxycarbonyl groups, thiocarboxy groups, and thioester groups, with monovalent groups containing a carbonyl group having 1 to 6 carbon atoms being preferred.

An acyl group is a substituent in which a carbonyl group is linked to an alkyl group, an alkenyl group, or an aryl group. The total number of carbon atoms (one) derived from the carbonyl group of the acyl group and the number of carbon atoms derived from the alkyl group, alkenyl group, or aryl group is preferably 2 to 20, more preferably 2 to 10, and even more preferably 2 to 6. Examples of acyl groups include an acetyl group, a propionyl group, a butylcarbonyl group, a vinylcarbonyl group, and a benzoyl group.

The amide group includes an amide group (-CONH ₂ ) having no substituent on the nitrogen atom, and an amide group in which some or all of the hydrogen atoms bonded to the nitrogen atom are substituted with carbon atoms. The number of carbon atoms in the amide group, calculated as the total number of the carbon atom (1) derived from the carbonyl group and the number of carbon atoms substituted on the nitrogen atom, is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 5. Examples of the amide group include an unsubstituted amide group, an N-methylamide group, an N-ethylamide group, an N-phenylamide group, an N,N-dimethylamide group, and an N-methyl-N-phenylamide group.

An alkoxycarbonyl group is a substituent in which a carbonyl group and an alkoxy group are linked, and is also called an ester group. The total number of carbon atoms (1) derived from the carbonyl group and the number of carbon atoms derived from the alkoxy group is preferably 2 to 20, more preferably 2 to 10, and even more preferably 2 to 6. Examples of alkoxycarbonyl groups include methoxycarbonyl groups, ethoxycarbonyl groups, butoxycarbonyl groups, and phenoxycarbonyl groups.

A thioester group is a substituent in which a carbonyl group is linked to an alkylthio group or an arylthio group. The total number of carbon atoms (one) derived from the carbonyl group and the number of carbon atoms derived from the alkylthio group or the arylthio group is preferably 2 to 20, more preferably 2 to 10, and even more preferably 2 to 6. Examples of thioester groups include a methylthiocarbonyl group, an ethylthiocarbonyl group, a butylthiocarbonyl group, and a phenylthiocarbonyl group.

Also, the monovalent group containing a carbonyl group may be a substituent in which one or more hydrogen atoms of an alkyl group are replaced with a carbonyl group. Examples of such a substituent include a 2-acetoxyethyl group, a 2-acetoethyl group, and a 2-(acetoacetoxy)ethyl group.

The alkylthio group is preferably an alkylthio group having 1 to 20 carbon atoms, more preferably an alkylthio group having 1 to 10 carbon atoms, and even more preferably an alkylthio group having 1 to 5 carbon atoms. Examples of alkylthio groups include methylthio groups, ethylthio groups, propylthio groups, and isopropylthio groups.

The arylthio group is preferably an arylthio group having 1 to 20 carbon atoms, more preferably an arylthio group having 3 to 10 carbon atoms, and even more preferably an arylthio group having 6 to 10 carbon atoms. Examples of arylthio groups include a phenylthio group and a tolylthio group.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, the following compounds are preferably used as component A1: methyl 2-phenylisobutyrate, 2-phenylisobutyric acid, 2-isopropylhydroquinone, 2-isopropyl-4-methoxyphenol, 2-methyl-2-phenylpropionamide, 2-(2-hydroxy-5-methoxyphenyl)-2-methylpropionic acid, 2-(2-methoxy-5-hydroxyphenyl)-2-methylpropionic acid, 2-(2,5-dihydroxyphenyl)-2-methylpropionic acid, methyl 2-(2-hydroxy-5-methoxyphenyl)-2-methylpropionate, methyl 2-(2-methoxy-5-hydroxyphenyl)-2-methylpropionate, or 2-(2,5-dihydroxyphenyl)-2-methylpropionic acid. )-2-methylpropionic acid methyl is preferred, 2-phenylisobutyric acid methyl, 2-phenylisobutyric acid, 2-isopropylhydroquinone, 2-isopropyl-4-methoxyphenol, 2-(2-hydroxy-5-methoxyphenyl)-2-methylpropionic acid, 2-(2-methoxy-5-hydroxyphenyl)-2-methylpropionic acid are more preferred, 2-phenylisobutyric acid methyl, 2-phenylisobutyric acid, 2-isopropylhydroquinone, 2-isopropyl-4-methoxyphenol, 2-(2-hydroxy-5-methoxyphenyl)-2-methylpropionic acid are even more preferred, and 2-phenylisobutyric acid methyl, 2-phenylisobutyric acid, 2-isopropylhydroquinone, 2-isopropyl-4-methoxyphenol are particularly preferred.

Component A1 may be one type or two or more types.

(Component B)
The methacrylic acid-containing composition according to the first aspect contains component B, which is a polymerization inhibitor. The polymerization inhibitor means a compound having a function of suppressing the polymerization reaction of methacrylic acid. Examples of the polymerization inhibitor include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, the polymerization reaction of methacrylic acid due to a radical polymerization mechanism can be suppressed from proceeding during storage of methacrylic acid. In addition, component B can trap the above-mentioned hydroxyl radicals generated during storage of methacrylic acid. That is, when the methacrylic acid-containing composition contains component B in addition to component A1, the amount of hydroxyl radicals can be reduced by two different mechanisms, that is, the generation of hydroxyl radicals can be suppressed by component A1 and the hydroxyl radicals generated by component B can be removed. Therefore, it is considered that the reduction of component B and the generation of decomposition products can be efficiently suppressed.

Phenol-based compounds that serve as polymerization inhibitors include alkylphenols, hydroxyphenols, aminophenols, nitrophenols, nitrosophenols, alkoxyphenols, and tocopherols.

Examples of alkylphenols include o-cresol, m-cresol, p-cresol, 2-t-butyl-4-methylphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, 2,2'-methylene-bis(6-t-butyl-4-methylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and 3,5-di-t-butyl-4-hydroxytoluene.

Hydroxyphenols include, for example, hydroquinone, 2-methylhydroquinone, 2-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,6-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone, 2-t-butylmethoxyhydroquinone, 2,3,5-trimethylhydroquinone, 2,5-dichlorohydroquinone, 1,2-dihydroxybenzene, 2-acetylhydroquinone, 4-methylcatechol, 4-t-butylcatechol, 2-methylresorcinol, 4-methylresorcinol, and 2,3-dihydroxyacetophenone.

Examples of aminophenols include o-aminophenol, m-aminophenol, p-aminophenol, 2-(N,N-dimethylamino)phenol, and 4-(ethylamino)phenol.

Examples of nitrophenols include o-nitrophenol, m-nitrophenol, p-nitrophenol, and 2,4-dinitrophenol.
Examples of nitrosophenols include o-nitrosophenol, m-nitrosophenol, p-nitrosophenol, α-nitroso-β-naphthol, and the like.

Examples of alkoxyphenols include 2-methoxyphenol, 2-ethoxyphenol, 2-isopropoxyphenol, 2-t-butoxyphenol, 4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol, 4-t-butoxyphenol, 4-heptoxyphenol, hydroquinone monobenzyl ether, t-butyl-4-methoxyphenol, di-t-butyl-4-methoxyphenol, pyrogallol-1,2-dimethyl ether, and hydroquinone monobenzoate.

Examples of tocopherols include α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.

Examples of polymerization inhibitors that are quinone compounds include p-benzoquinone, chloro-p-benzoquinone, 2,5-dichloro-p-benzoquinone, 2,6-dichloro-p-benzoquinone, tetrachloro-p-benzoquinone, tetrabromo-p-benzoquinone, 2,3-dimethyl-p-benzoquinone, 2,5-dimethyl-p-benzoquinone, methoxy-p-benzoquinone, and methyl-p-benzoquinone.

Examples of polymerization inhibitors that are nitrobenzene-based compounds include nitrobenzene, o-dinitrobenzene, m-dinitrobenzene, p-dinitrobenzene, 2,4-dinitrotoluene, dinitrodurene, and 2,2-diphenyl-1-picrylhydrazyl.

Examples of polymerization inhibitors that are N-oxyl compounds include 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, piperidine-1-oxyl, 4-(dimethylamino)-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-amino-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-ethanoloxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, and 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl. Sil, 2,2,5,5-tetramethyl-piperidine-N-oxyl, 3-amino-2,2,5,5-tetramethyl-piperidine-N-oxyl, 4,4',4''-tris(2,2,6,6-tetramethyl-piperidine-N-oxyl)phosphite, 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxyl, pyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-1-oxa-3-azacyclopentyl-3-oxy, 2,2,5,5-tetramethyl-3-pyrrolinyl-1-oxy-3-carboxylic acid, 2,2,3,3,5,5,6,6-octamethyl-1,4-diazacyclohexyl-1,4-dioxy, di-tert-butyl nitroxide, di-tert-amyl nitroxide, etc.

Examples of polymerization inhibitors that are amine compounds include N,N-diphenylamine, alkylated diphenylamine, 4,4'-dicumyl-diphenylamine, 4,4'-dioctyldiphenylamine, 4-aminodiphenylamine, p-nitrosodiphenylamine, N-nitrosodinaphthylamine, N-nitrosodiphenylamine, N-nitrosophenylnaphthylamine, N-nitrosophenylhydroxylamine, N,N'-dialkyl-p-phenylenediamine (wherein the alkyl groups may be the same or different, each independently comprise 1 to 4 carbon atoms, and may be linear or branched), N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, Examples include N,N'-di-2-naphthyl-p-phenylenediamine, N,N-diethylhydroxylamine, 1,4-benzenediamine, N-(1,4-dimethylpentyl)-N'-phenyl-1,4-benzenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-1,4-benzenediamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, aldol-α-naphthylamine, N-phenyl-β-naphthylamine, 4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, and 1-hydroxy-4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

Examples of polymerization inhibitors that are phosphorus-containing compounds include triphenylphosphine, triphenyl phosphite, triethyl phosphite, tris(isodecyl)phosphite, tris(tridecyl)phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, phenyl di(tridecyl)phosphite, diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl tridecyl phosphite, phosphonic acid [1,1-diphenyl-4,4'-diylbistetrakis-2,4-bis(1,1-dimethylethyl)phenyl] ester, tris(nonylphenyl)phosphite, 4,4'-isopropylidenediphenol alkyl phosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(biphenyl)phosphite, and distearyl pentaerythritol. Examples of such phosphates include tetra(tridecyl)-4,4'-butylidenebis(3-methyl-6-tert-butylphenol)diphosphite, hexa(tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butanetriphosphite, 3,5-di-tert-butyl-4-hydroxybenzyl phosphate diethyl ester, sodium bis(4-tert-butylphenyl)phosphate, sodium 2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate, and 1,3-bis(diphenoxyphosphonyloxy)benzene.

Examples of polymerization inhibitors that are sulfur-containing compounds include diphenyl sulfide, phenothiazine, 3-oxophenothiazine, 5-oxophenothiazine, phenothiazine dimer, 1,4-dimercaptobenzene, 1,2-dimercaptobenzene, 2-mercaptophenol, 4-mercaptophenol, 2-(methylthio)phenol, 3,7-bis(dimethylamino)phenothiazinium chloride, and sulfur (element).

An example of a polymerization inhibitor that is an iron-containing compound is iron(III) chloride.

Examples of polymerization inhibitors that are copper-containing compounds include copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, copper acetate, copper thiocyanate, copper nitrate, copper chloride, copper carbonate, copper hydroxide, copper acrylate, and copper methacrylate.

Polymerization inhibitors that are manganese-containing compounds include manganese dialkyldithiocarbamate (wherein the alkyl groups are methyl, ethyl, propyl, or butyl groups and may be the same or different), manganese diphenyldithiocarbamate, manganese formate, manganese acetate, manganese octanoate, manganese naphthenate, manganese permanganate, and manganese salts of ethylenediaminetetraacetic acid.

Among the above, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, and for example, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenylphosphite, and phenothiazine. It is more preferable that component B is a phenolic compound, and for example, it is more preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol. Component B is more preferably at least one polymerization inhibitor selected from the group consisting of, for example, hydroquinone, 4-methoxyphenol, and 2,6-di-t-butyl-4-methylphenol. Component B is particularly preferably at least one polymerization inhibitor selected from the group consisting of, for example, hydroquinone and 4-methoxyphenol.

There may be one type or two or more types of component B. When two or more types of component B are contained, the total amount is regarded as the content of component B.
When a methacrylic acid-containing composition contains a compound corresponding to both component A1 and component B, the compound is regarded as component B. That is, the methacrylic acid-containing composition must contain a component A1 other than the compound. When two or more compounds corresponding to both component A1 and component B are contained, the compound having the highest molar concentration in the methacrylic acid-containing composition is regarded as component B, and the other compounds are regarded as component A1.

(Concentration of Component A1 and Component B)
When the concentration of component A1 is _M (μmol/L) and the concentration of component B is _M (μmol/ _L ), from the viewpoint of efficiency in suppressing consumption of the polymerization inhibitor, _M /M is preferably 0.0005 to 100, more preferably 0.001 to 85, even more preferably 0.005 to 70, and particularly preferably 0.005 to 60.

M _A1 is preferably 1 to 500,000 μmol/L. By M _A1 being 1 μmol/L or more, the effect of suppressing consumption of the polymerization inhibitor can be sufficiently obtained. In addition, by M _A1 being 500,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the first aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A1 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, more preferably 50 μmol/L or more, and particularly preferably 70 μmol/L or more. The upper limit of M _A1 is more preferably 450,000 μmol/L or less, even more preferably 400,000 μmol/L or less, particularly preferably 350,000 μmol/L or less, and particularly preferably 300,000 μmol/L or less.

M _B is preferably 1 to 50,000 μmol/L. By having M _B of 1 μmol/L or more, the effect of suppressing consumption of the polymerization inhibitor can be sufficiently obtained. Furthermore, by having M _B of 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the first aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1000 μmol/L or more, and especially preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 40,000 μmol/L or less, even more preferably 30,000 μmol/L or less, and particularly preferably 25,000 μmol/L or less.

(Methacrylic acid concentration)
The concentration of methacrylic acid in the methacrylic acid-containing composition according to the first embodiment is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the first embodiment can be reduced, and adverse effects on the physical properties of the polymer can be prevented. In addition, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, particularly preferably 99.50% or more, and most preferably 99.80% by mass or more.

(Component C)
The methacrylic acid-containing composition according to the first aspect may further contain component C, which is another compound, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, methacrylic acid may contain diacetyl as an impurity, and from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L or less, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A1, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A1, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A1, it can be determined that the methacrylic acid-containing composition contains component A1. If a standard specimen of component A1 is not available, it can be determined that the peak is a peak of component A1 when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A1 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A1. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying using the area percentage method, and correcting using the moisture concentration quantified with a Karl Fischer moisture meter. The concentration of component A1 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition, and quantifying using the internal standard method. If a standard specimen of component A1 cannot be obtained and cannot be quantified by the internal standard method, GC-FID measurement is performed on any organic compound with a known concentration under the same conditions as the methacrylic acid-containing composition, and the concentration of component A1 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A1 , _S is the peak area of component A1, S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A1.
In addition, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water can be confirmed by the Karl Fischer method.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the first aspect includes a method of adding component A1 and component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A1 and component B may be commercially available products, or those synthesized by a known method may be used. When a commercially available product containing component B is used as methacrylic acid, component B contained in the commercially available product may be used as component B of the present invention, or component B may be added additionally. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, component A1 or component B may be added to the raw material or during the process of the production process to produce a methacrylic acid-containing composition. In addition, when component A1 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A1 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the first aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100°C, and the heating time is preferably 1 to 24 hours. In the present invention, the quality stability of a methacrylic acid-containing composition during storage was evaluated by the amount of polymerization inhibitor reduction when the methacrylic acid-containing composition was stored at 25°C for 21 days.

[Method for producing methacrylic acid ester according to the first aspect]
The method for producing a methacrylic acid ester according to the first aspect includes a step of esterifying methacrylic acid in the methacrylic acid-containing composition according to the first aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the first embodiment]
The method for producing a methacrylic acid polymer according to the first aspect includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the first aspect.

The polymerizable composition may further contain a monomer copolymerizable with methacrylic acid and other additives, if necessary.

Examples of monomers copolymerizable with methacrylic acid include the following.
Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, or benzyl methacrylate;
acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, or 2-ethylhexyl acrylate;
Unsaturated carboxylic acids such as acrylic acid, maleic acid, or itaconic acid;
Unsaturated carboxylic acid anhydrides such as maleic anhydride or itaconic anhydride;
Maleimides such as N-phenylmaleimide or N-cyclohexylmaleimide;
Hydroxy group-containing vinyl monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate;
Vinyl esters such as vinyl acetate or vinyl benzoate;
Vinyl chloride, vinylidene chloride and their derivatives;
Nitrogen-containing vinyl monomers such as methacrylamide or acrylonitrile;
Epoxy group-containing monomers such as glycidyl acrylate or glycidyl methacrylate;
Aromatic vinyl monomers such as styrene or α-methylstyrene;
Alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, or 1,6-hexanediol di(meth)acrylate;
polyoxyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, or neopentyl glycol di(meth)acrylate;
Vinyl monomers having two or more ethylenically unsaturated bonds in the molecule, such as divinylbenzene;
an unsaturated polyester prepolymer obtained from at least one polycarboxylic acid including an ethylenically unsaturated polycarboxylic acid and at least one diol;
A vinyl ester prepolymer obtained by modifying the terminal epoxy group with an acrylic acid.

Among the above, the monomer copolymerizable with methacrylic acid is preferably at least one selected from the group consisting of methacrylic acid esters and acrylic acid esters. The monomer copolymerizable with methacrylic acid is more preferably a methacrylic acid ester, and particularly preferably methyl methacrylate.

The monomer copolymerizable with methacrylic acid may be one type or two or more types. In addition, when component A1 is a monomer copolymerizable with methacrylic acid, component A1 may be used as a monomer copolymerizable with methacrylic acid, or a monomer copolymerizable with methacrylic acid may be used separately from component A1.

In the polymerizable composition, the content of the monomer copolymerizable with methacrylic acid is preferably 50.00 to 99.99 parts by mass per 100 parts by mass of the polymerizable composition. The lower limit of the content of the monomer copolymerizable with methacrylic acid is more preferably 60 parts by mass or more per 100 parts by mass of the polymerizable composition, even more preferably 70 parts by mass or more, particularly preferably 80 parts by mass or more, and most preferably 90 parts by mass or more. The upper limit of the content of the monomer copolymerizable with methacrylic acid is more preferably 99.9 parts by mass or less per 100 parts by mass of the polymerizable composition, even more preferably 99 parts by mass or less.

Other additives include, for example, polymerization initiators, chain transfer agents, release agents, lubricants, plasticizers, antioxidants, antistatic agents, light stabilizers, UV absorbers, flame retardants, flame retardant assistants, polymerization inhibitors, fillers, pigments, dyes, silane coupling agents, leveling agents, defoamers, and fluorescent agents. The other additives may be of one type or two or more types.

As the other additives, a polymerization initiator is preferable. Examples of the polymerization initiator include the following.
azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2-2'-azobis(2-methylpropane), 1,1'-azobis(cyclohexanecarbonitrile), and dimethyl-2,2'-azobisisobutyrate;
Benzoyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxybenzoate, t-hexylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyacetate, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxylaurate, organic peroxides such as 1,1,3,3-tetramethylbutyl peroxyethylhexanoate, 1,1,2-trimethylpropyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxyisopropyl monocarbonate, 1,1,2-trimethylpropyl peroxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxyisononaate, 1,1,2-trimethylpropyl peroxyisononaate, di-t-butyl peroxide, di-t-hexyl peroxide, lauroyl peroxide, and dilauroyl peroxide;
Persulfate compounds such as potassium persulfate;
Redox polymerization initiator.

Among the above, from the viewpoints of storage stability and reactivity with methacrylic acid and copolymerizable monomers, the polymerization initiator is preferably at least one selected from the group consisting of azo compounds and organic peroxides.
The amount of the polymerization initiator used is preferably 0.0001 to 1 part by mass per 100 parts by mass of the total of methacrylic acid and the monomer copolymerizable with methacrylic acid.

Examples of the polymerization method for the polymerizable composition include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.
The polymerization temperature is preferably 125 to 210° C. This allows an appropriate polymerization rate to be obtained. The lower limit of the polymerization temperature is more preferably 130° C. or more, and the upper limit is more preferably 180° C. or less. The polymerization time is not particularly limited, and can be, for example, 0.5 to 24 hours.

[Methacrylic acid-containing composition according to the second aspect]
In the first embodiment of the second aspect, the methacrylic acid-containing composition contains methacrylic acid, a component A21 which is a compound represented by the following formula (21), and a polymerization inhibitor (component B). The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In formula (21), R ^1b , R ^2b , R ^3b and R ^4b each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^1b and R ^2b , and R ^3b and R ^4b may be linked to each other to form a ring.
In addition, the methacrylic acid-containing composition may contain other compounds (component C) and water as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the second aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A21)
The first embodiment of the methacrylic acid-containing composition according to the second aspect contains component A21, which is a compound represented by the formula (21). The coexistence of component A21 and component B described later can suppress the decomposition of the polymerization inhibitor during storage of the methacrylic acid-containing composition. The reason for this is presumed to be as follows.

Methacrylic acid is known to polymerize due to radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes into another compound when trapping the radicals, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated when oxygen molecules absorb ultraviolet light derived from sunlight. Component A21 has an aromatic ring and absorbs ultraviolet light, and the absorption wavelength changes depending on the type of substituent. Component A21, which has a structure represented by the above formula (21), can absorb ultraviolet light of a wide range of wavelengths. Therefore, when the methacrylic acid-containing composition contains component A21, ultraviolet light of a wide range of wavelengths is absorbed, and the generation of hydroxyl radicals caused by oxygen molecules absorbing ultraviolet light is suppressed. This reduces the number of radicals that component B needs to trap, which can suppress the decrease in the concentration of component B and the generation of decomposition products.

The molecular weight of component A21 is preferably 1000 or less. This increases the number of pyrazine rings per unit mass of component A21, making it possible to obtain the effects of the present invention with a small amount of component A21. The molecular weight of component A21 is more preferably 800 or less, even more preferably 600 or less, and particularly preferably 400 or less.

In the formula (21), R ^1b , R ^2b , R ^3b and R ^4b each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^1b , R ^2b , R ^3b and R ^4b may be the same or different.

From the viewpoint of increasing the absorbance of ultraviolet light and suppressing the generation of hydroxyl radicals, R ^1b , R ^2b , R ^3b and R ^4b are preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms or an arylthio group having 6 to 10 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms or an alkylthio group having 6 to 10 carbon atoms, still more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a methylthio group, a methoxy group, a carboxy group, a carbomethoxy group or a hydroxymethyl group, and particularly preferably a hydrogen atom, a methyl group, an isopropyl group, a methylthio group, a methoxy group, a carboxy group, a carbomethoxy group or a hydroxymethyl group.

The alkyl group is a chain (straight-chain or branched) alkyl group or a cyclic alkyl group. An alkyl group having 1 to 20 carbon atoms is preferred, an alkyl group having 1 to 10 carbon atoms is more preferred, and an alkyl group having 1 to 5 carbon atoms is even more preferred. Examples of chain alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, hexyl, octyl, decyl, hydroxymethyl, 1-hydroxyethyl, and 2-hydroxyethyl groups, with methyl, ethyl, n-propyl, and isopropyl groups being preferred. Examples of cyclic alkyl groups include cyclopentyl, cyclohexyl, and cyclooctyl groups.

The alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 10 carbon atoms, even more preferably an alkoxy group having 1 to 6 carbon atoms, and particularly preferably an alkoxy group having 1 to 5 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, n-pentoxy, isopentoxy, and phenoxy groups.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, the following compounds are used as component A21: 2,3,5,6-tetramethylpyrazine, pyrazine, 2,3,5-trimethylpyrazine, 2-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,5-dimethylpyrazine, 2-aminopyrazine, 2-methylpyrazine, 2-methylpyrazine, 2-methyl-3- ... Hydroquinoxaline, phenazine, or 1,2,3,4,6,7,8,9-octahydrophanazine is preferred, 2,3,5,6-tetramethylpyrazine, pyrazine, 2,3,5-trimethylpyrazine, 2-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,5-dimethylpyrazine, 2-aminopyrazine, 2-methylpyrazinecarboxylate, 2-(methylthio)pyrazine, 2-pyrazinemethanol, quinoxaline, or 2-vinylpyrazine is more preferred, and 2,3,5,6-tetramethylpyrazine, pyrazine, 2,3,5-trimethylpyrazine, 2-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,5-dimethylpyrazine, methylpyrazinecarboxylate, 2-(methylthio)pyrazine, or 2-pyrazinemethanol is even more preferred.

Component A21 may be one type or two or more types.

(Component B)
In the first embodiment of the second aspect, the methacrylic acid-containing composition contains component B. Component B is a compound that acts as a polymerization inhibitor. In this specification, a polymerization inhibitor means a compound that has a function of suppressing the polymerization reaction of methacrylic acid. Examples of polymerization inhibitors include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, it is possible to suppress the progress of the polymerization reaction of methacrylic acid by a radical polymerization mechanism during storage of methacrylic acid. In addition, component B can trap the above-mentioned hydroxyl radicals generated during storage of methacrylic acid. That is, when the methacrylic acid-containing composition contains component B in addition to component A21, the amount of hydroxyl radicals can be reduced by two different mechanisms, that is, the generation of hydroxyl radicals can be suppressed by component A21 and the hydroxyl radicals generated by component B can be removed. Therefore, it is considered that the decrease of component B can be efficiently suppressed.

Among the above, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, and for example, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenylphosphite, and phenothiazine. It is more preferable that component B is a phenolic compound, and for example, it is more preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol. Component B is more preferably a phenolic compound, and even more preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone and 4-methoxyphenol.

Component B may be one type or two or more types.
When a methacrylic acid-containing composition contains a compound corresponding to both component A21 and component B, the compound is regarded as component B. That is, the methacrylic acid-containing composition must contain a component A21 other than the compound. When two or more compounds corresponding to both component A21 and component B are contained, the compound having the highest molar concentration in the methacrylic acid-containing composition is regarded as component B, and the other compounds are regarded as component A21.

(Concentration of Component A21 and Component B)
When the concentration of component A21 is _M (μmol/L) and the concentration of component B is _M (μmol/ _L ), from the viewpoint of inhibiting the production of pyruvic acid, _M /M is preferably 0.005 to 100, more preferably 0.01 to 80, even more preferably 0.05 to 60, and particularly preferably 0.1 to 40.

M _A21 is preferably 1 to 50,000 μmol/L. By M _A21 being 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. In addition, by M _A21 being 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the second aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A21 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, particularly preferably 50 μmol/L or more, and especially preferably 60 μmol/L or more. The upper limit of M _A21 is more preferably 30,000 μmol/L or less, and even more preferably 10,000 μmol/L or less. Particularly preferably 5,000 μmol/L or less, especially preferably 2,500 μmol/L or less, and most preferably 500 μmol/L or less.

M _B is preferably 1 to 50,000 μmol/L. By M _B being 1 μmol/L or more, the effect of suppressing the analysis of the polymerization inhibitor can be sufficiently obtained. Furthermore, by M _B being 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the second aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1000 μmol/L or more, especially preferably 1500 μmol/L or more, and most preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 10,000 μmol/L or less, even more preferably 5,000 μmol/L or less, especially preferably 3,000 μmol/L or less, and especially preferably 2,500 μmol/L or more.

(Methacrylic acid concentration)
In the first embodiment, the concentration of methacrylic acid in the methacrylic acid-containing composition according to the second aspect is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the second aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. In addition, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, particularly preferably 99.50% or more, and most preferably 99.80% by mass or more.

(Component C)
The first embodiment of the methacrylic acid-containing composition according to the second aspect may further contain another compound, component C, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, methacrylic acid may contain diacetyl as an impurity, but from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L or less, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A21, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A21, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A21, it can be determined that the methacrylic acid-containing composition contains component A21. If a standard specimen of component A21 is not available, it can be determined that the peak is a peak of component A21 when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A21 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A21. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying it using the area percentage method, and correcting it using the moisture concentration quantified by a Karl Fischer moisture meter. The concentration of component A21 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition, and quantifying it using the internal standard method. If a standard specimen of component A21 cannot be obtained and cannot be quantified by the internal standard method, GC-FID measurement is performed on any organic compound with a known concentration under the same conditions as the methacrylic acid-containing composition, and the concentration of component A21 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A21 , S is the peak area of component _A21 , S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A21 above.
Furthermore, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water therein can be confirmed by the Karl Fischer method.

(Component B)
In the second embodiment of the second aspect, the methacrylic acid-containing composition preferably contains component B. The preferred embodiment of component B is the same as that of the first embodiment. In addition, component B may be one type or two or more types.

(Concentration of Component B)
The preferred embodiment of _MB is the same as that of the first embodiment.

(Methacrylic acid concentration)
The preferred concentration of methacrylic acid is the same as in the first embodiment.

(Component C)
The details and preferred embodiments of component C are the same as those of the first embodiment.

(Analysis of methacrylic acid-containing composition)
The method for confirming that the methacrylic acid-containing composition contains component B, component C and water, and the method for measuring the concentrations of methacrylic acid, component B, component C and water are the same as those in the first embodiment.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the second aspect includes a method of adding component A21 and, if necessary, component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A21 and component B may be commercially available products, or products synthesized by a known method may be used. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, component A21 or component B may be added as a raw material or during the process of the production process to produce a methacrylic acid-containing composition. In addition, when component A21 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A21 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the second aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100°C, and the heating time is preferably 1 to 24 hours. In the present invention, the quality stability of the methacrylic acid-containing composition during storage was evaluated from the amount of polymerization inhibitor reduction when the methacrylic acid-containing composition was stored at 25°C for 21 days.

[Methacrylic acid ester manufacturing method]
The method for producing a methacrylic acid ester according to the second aspect includes a step of esterifying the methacrylic acid-containing composition according to the second aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the second embodiment]
The method for producing a methacrylic acid polymer according to the second aspect includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the second aspect.

The polymerizable composition may contain, as necessary, a monomer copolymerizable with methacrylic acid and other additives.

The monomer copolymerizable with methacrylic acid may be one type or two or more types. In addition, when component A21 is a monomer copolymerizable with methacrylic acid, component A21 may be used as a monomer copolymerizable with methacrylic acid, or a monomer copolymerizable with methacrylic acid may be used separately from component A21.

As the other additives, a polymerization initiator is preferred. Furthermore, the polymerizable composition may further contain a chain transfer agent, a release agent, a lubricant, a plasticizer, an antioxidant, an antistatic agent, a light stabilizer, an ultraviolet absorber, a flame retardant, a flame retardant assistant, a polymerization inhibitor, a filler, a pigment, a dye, a silane coupling agent, a leveling agent, an antifoaming agent, a fluorescent agent, etc., as necessary. The other additives may be one type or two or more types.

Examples of the polymerization initiator include the following.
azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2-2'-azobis(2-methylpropane), 1,1'-azobis(cyclohexanecarbonitrile), and dimethyl-2,2'-azobisisobutyrate;
Benzoyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxybenzoate, t-hexylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyacetate, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxylaurate, organic peroxides such as 1,1,3,3-tetramethylbutyl peroxyethylhexanoate, 1,1,2-trimethylpropyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxyisopropyl monocarbonate, 1,1,2-trimethylpropyl peroxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutyl peroxyisononaate, 1,1,2-trimethylpropyl peroxyisononaate, di-t-butyl peroxide, di-t-hexyl peroxide, lauroyl peroxide, and dilauroyl peroxide;
Persulfate compounds such as potassium persulfate;
Redox polymerization initiator.

[Methacrylic acid-containing composition according to the third aspect]
The methacrylic acid-containing composition according to the third embodiment contains methacrylic acid and a component A3 which is a compound represented by the following formula (31). The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In formula (31), R ^1c , R ^2c , R ^3c , R ^4c , R ^5c , R ^6c and R ^7c independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group.
In addition, the methacrylic acid-containing composition may contain a polymerization inhibitor (component B), other compounds (component C) and water, so long as the concentration of methacrylic acid is 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the third aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A3)
The methacrylic acid-containing composition according to the third aspect contains a compound (component A3) represented by the formula (31). By containing component A3 in the methacrylic acid-containing composition, decomposition of the polymerization inhibitor during storage of the methacrylic acid-containing composition can be suppressed. The reason for this is presumed to be as follows.

Methacrylic acid is known to polymerize due to radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes the radicals into other compounds when trapping them, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated when oxygen molecules absorb ultraviolet light derived from sunlight. Component A3 is a π-conjugated compound having a benzene ring, so it absorbs ultraviolet light, and the absorption wavelength changes depending on the type of substituent. Component A3 can absorb ultraviolet light of a wide range of wavelengths. Therefore, when a methacrylic acid-containing composition contains component A3, ultraviolet light of a wide range of wavelengths is absorbed, and the generation of hydroxyl radicals is suppressed. Therefore, the radicals that component B needs to trap are reduced, and the decrease in the concentration of component B and the generation of decomposition products can be suppressed.

The molecular weight of component A3 is preferably 2000 or less. By having a molecular weight of 2000 or less, the number of benzene rings per unit mass in component A3 can be increased, so that the effects of the present invention can be obtained with a small mass. The molecular weight of component A3 is more preferably 1600 or less, even more preferably 1200 or less, and particularly preferably 800 or less.

In formula (31), R ^1c , R ^2c , R ^3c , R ^4c , R ^5c , R ^6c and R ^7c each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^1c , R ^2c , R ^3c , R ^4c , R ^5c , R ^6c and R ^7c may be the same or different.

When R ^1c , R ^2c , R ^3c , R ^4c , R ^5c , R ^6c and R ^7c satisfy the above conditions, the π-conjugated system of ^component ^A3 is maintained and ultraviolet light of a ^wide ^wavelength can ^be absorbed, so that the generation of hydroxyl radicals is suppressed and the effects of the present invention can be ^obtained . ^7c is preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a monovalent group containing a carbonyl group having 1 to 6 carbon atoms; more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxy group, an alkoxy group having 1 to 5 carbon atoms, a carboxy group, or an alkoxycarbonyl group having 2 to 6 carbon atoms; even more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a hydroxy group; even more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an i-butyl group, a t-butyl group, or a hydroxy group; even more preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl ... and most preferably a hydrogen atom, a methyl group, or a hydroxy group.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, the following compounds are preferred as component A3: t-butylphenyl ether, isopropylphenyl ether, 1-isopropoxy-3-methylbenzene, 4-isopropoxyphenol, 1-t-butoxy-4-methylbenzene, 2-(2,4-dimethyl-6-t-butylphenoxy)-2-methylpropionic acid, 2-(2,6-di-t-butyl-4-methylphenoxy)-2-methylpropionic acid, 2-(4-methoxyphenoxy)-2-methylpropionic acid, 2-(4-hydroxyphenoxy)-2-methylpropionic acid, 2-(2,4-dimethyl-6-t-butyl ... butylphenoxy)-2-methylpropionic acid methyl, 2-(2,6-di-t-butyl-4-methylphenoxy)-2-methylpropionic acid methyl, 2-(4-methoxyphenoxy)-2-methylpropionic acid methyl, or 2-(4-hydroxyphenoxy)-2-methylpropionic acid methyl are preferred, t-butylphenyl ether, isopropylphenyl ether, 1-isopropoxy-3-methylbenzene, 4-isopropoxyphenol, or 2-(4-methoxyphenoxy)-2-methylpropionic acid are more preferred, and t-butylphenyl ether and 2-(4-methoxyphenoxy)-2-methylpropionic acid are even more preferred.

Component A3 may be one type or two or more types.

(Component B)
The methacrylic acid-containing composition according to the third aspect preferably contains a polymerization inhibitor (component B). In this specification, the polymerization inhibitor means a compound having a function of suppressing the polymerization reaction of methacrylic acid. Examples of the polymerization inhibitor include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, the polymerization reaction of methacrylic acid due to a radical polymerization mechanism can be suppressed from proceeding during storage of methacrylic acid. In addition, component B can trap the above-mentioned hydroxyl radicals generated during storage of methacrylic acid. That is, when the methacrylic acid-containing composition contains component B in addition to component A3, the amount of hydroxyl radicals can be reduced by two different mechanisms, that is, the generation of hydroxyl radicals can be suppressed by component A3 and the hydroxyl radicals generated by component B can be removed. Therefore, it is considered that the reduction of component B and the generation of decomposition products can be efficiently suppressed.

Among the above, from the viewpoint of the quality stability during storage of the methyl methacrylate-containing composition, component B is preferably at least one polymerization inhibitor selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, and is preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenyl phosphite, and phenothiazine. Component B is more preferably a phenolic compound, and is more preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol. Component B is particularly preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone and 4-methoxyphenol.

Component B may be one type or two or more types.
When a methacrylic acid-containing composition contains a compound corresponding to both component A3 and component B, the compound is regarded as component A3. In other words, when a methacrylic acid-containing composition contains component A3 and component B, it means that the composition contains a component B other than the compound. When two or more compounds corresponding to both component A3 and component B are contained, the compound having the highest molar concentration in the methacrylic acid-containing composition is regarded as component A3, and the other compounds are regarded as component B.

(Concentration of Component A3 and Component B)
When the concentration of component A3 is _M (μmol/L) and the concentration of component B is _M (μmol/ _L ), from the viewpoint of the efficiency of inhibiting the production of methacrylic acid dimer and pyruvic acid, M/ _M is preferably 0.005 to 100, and more preferably 0.05 to 10.

M _A3 is preferably 1 to 50,000 μmol/L. By M _A3 being 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. In addition, by M _A3 being 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the third aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A3 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, even more preferably 50 μmol/L or more, even more preferably 55 μmol/L or more, and particularly preferably 60 μmol/L or more. The upper limit of M _A3 is more preferably 25,000 μmol/L or less, even more preferably 10,000 μmol/L or less, and particularly preferably 7,500 μmol/L or less.

It is preferable that M _B is 1 to 50,000 μmol/L. By having M _B of 1 μmol/L or more, the effect of suppressing the production of methacrylic acid dimers and pyruvic acid can be sufficiently obtained. In addition, by having M _B of 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the third aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1500 μmol/L or more, and most preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 45,000 μmol/L or less, further preferably 40,000 μmol/L or less, particularly preferably 35,000 μmol/L or less, even more preferably 30,000 μmol/L or less, and most preferably 25,000 μmol/L or less.

(Methacrylic acid concentration)
The concentration of methacrylic acid in the methacrylic acid-containing composition according to the third aspect is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the third aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. Furthermore, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, and particularly preferably 99.50% or more.

(Component C)
The methacrylic acid-containing composition according to the third aspect may further contain component C, which is another compound, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, methacrylic acid may contain diacetyl as an impurity, and from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L or less, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A3, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A3, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A3, it can be determined that the methacrylic acid-containing composition contains component A3. If a standard specimen of component A3 is not available, it can be determined that the peak is a component A3 peak when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A3 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A3. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying it using the area percentage method, and correcting it using the moisture concentration quantified by a Karl Fischer moisture meter. The concentration of component A3 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition and quantifying it using the internal standard method. If a standard specimen of component A3 cannot be obtained and it cannot be quantified by the internal standard method, any organic compound with a known concentration can be measured by GC-FID measurement under the same conditions as the methacrylic acid-containing composition, and the concentration of component A3 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A3 , _S is the peak area of component A3, S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A3 above.
Furthermore, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water therein can be confirmed by the Karl Fischer method.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the third aspect includes a method of adding component A3 to methacrylic acid, and preferably a method of adding component A3 and component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A3 and component B may be commercially available products, or products synthesized by a known method may be used. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, the methacrylic acid-containing composition may be produced by adding component A3 or component B in the middle of the raw material or production process. In addition, when component A3 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A3 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the third aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100°C, and the heating time is preferably 1 to 24 hours. In the present invention, the quality stability of a methacrylic acid-containing composition during storage was evaluated by the amount of polymerization inhibitor reduction when the methacrylic acid-containing composition was stored at 25°C for 21 days.

[Methacrylic acid ester manufacturing method]
The method for producing a methacrylic acid ester according to the third aspect includes a step of esterifying the methacrylic acid-containing composition according to the third aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the third embodiment]
The method for producing a methacrylic acid polymer according to the third aspect includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the third aspect.

The monomer copolymerizable with methacrylic acid may be one type or two or more types. In addition, when component A3 is a monomer copolymerizable with methacrylic acid, component A3 may be used as a monomer copolymerizable with methacrylic acid, or a monomer copolymerizable with methacrylic acid may be used separately from component A3.

As the other additives, a polymerization initiator is preferred. Furthermore, the polymerizable composition may contain, as necessary, a chain transfer agent, a release agent, a lubricant, a plasticizer, an antioxidant, an antistatic agent, a light stabilizer, an ultraviolet absorber, a flame retardant, a flame retardant assistant, a polymerization inhibitor, a filler, a pigment, a dye, a silane coupling agent, a leveling agent, an antifoaming agent, a fluorescent agent, etc. The other additives may be of one type or two or more types.

[Methacrylic acid-containing composition according to the fourth aspect]
The methacrylic acid-containing composition according to the fourth aspect contains methacrylic acid, a compound (component A4) represented by the following formula (41), and a polymerization inhibitor (component B). The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In formula (41), R ^d represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and these groups may further have a substituent.
In addition, the methacrylic acid-containing composition may contain other compounds (component C) and water as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the fourth aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A4)
The methacrylic acid-containing composition according to the fourth aspect contains a compound (component A4) represented by the formula (41). By containing component A4 in the methacrylic acid-containing composition, decomposition of the polymerization inhibitor can be suppressed. The reason for this is presumed to be as follows.

It is known that methacrylic acid polymerizes due to radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes into another compound when trapping the radicals, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated by oxygen molecules absorbing ultraviolet light derived from sunlight. Since component A4 has weak basicity, the generation of hydroxyl ions (OH ⁻ ) takes precedence over hydroxyl radicals, and the generation of hydroxyl radicals is suppressed. Therefore, the radicals that component B needs to trap are reduced, and the decrease in the concentration of component B can be suppressed.

The molecular weight of component A4 is preferably 1000 or less. By having a molecular weight of 1000 or less, the number of cyano groups per unit mass in component A4 can be increased, so that the effects of the present invention can be obtained with a small mass. The molecular weight of component A4 is more preferably 800 or less, even more preferably 600 or less, and particularly preferably 400 or less.

R ^d in the formula (41) represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and these groups may further have a substituent.

When R ^d satisfies the above conditions, the weak basicity of component A4 and the reactivity with acidic substances and radicals are maintained, so that the effects of the present invention can be obtained. In addition, since it is a highly stable group, it is possible to prevent component A4 from changing into other compounds during storage. R ^d is preferably an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, or an aryl group having 6 to 8 carbon atoms. ^{R d} is more preferably a methyl group, an ethyl group, a vinyl group, an isopropenyl group, a phenyl group, a methylthiophenyl group, an acetoxyphenyl group, or a cyanophenyl group, further preferably a methyl group, an ethyl group, a vinyl group, an isopropenyl group, a methylthiophenyl group, an acetoxyphenyl group, or a cyanophenyl group, and particularly preferably a methyl group, an ethyl group, a vinyl group, an isopropenyl group, an acetoxyphenyl group, or a cyanophenyl group.

The alkyl group is a chain (straight-chain or branched) alkyl group or a cyclic alkyl group. Examples of chain alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, and isopentyl groups. Among these, methyl, ethyl, n-propyl, and isopropyl groups are preferred, and methyl or ethyl groups are more preferred. Examples of cyclic alkyl groups include cyclopropyl, cyclobutyl, and cyclopentyl groups.

The alkenyl group is a chain (straight-chain or branched) alkenyl group or a cyclic alkenyl group. Examples of chain alkenyl groups include vinyl groups, 1-propenyl groups, isopropenyl groups, 2-butenyl groups, 1,3-butadienyl groups, and 2-pentenyl groups. Among these, vinyl groups, 1-propenyl groups, and isopropenyl groups are preferred, and vinyl groups and isopropenyl groups are more preferred. Examples of cyclic alkenyl groups include cyclopropenyl groups, cyclobutenyl groups, and cyclopentenyl groups.

Aryl groups include heteroaryl groups containing oxygen, nitrogen, sulfur, etc. Examples of aryl groups include phenyl, mesityl, naphthyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, isoxazolyl, isothiazolyl, imidazolyl, oxazolyl, thiazolyl, thiadiazolyl, thienyl, triazolyl, tetrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrazolyl, pyrrolyl, furyl, furazanyl, isoquinolyl, isoindolyl, indolyl, quinolyl, pyridothiazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, benzotriazolyl, benzofuranyl, imidazopyridinyl, triazopyridinyl, and purinyl groups.

When R ^d is an alkyl group, alkenyl group, or aryl group having a substituent, examples of the substituent include an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group, and an arylthio group. Among these, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, and an alkylthio group are preferred, and a hydroxy group, a methoxy group, an amino group, an acetyl group, and a methylthio group are more preferred. The molecular weight of the substituent is preferably 200 or less, more preferably 100 or less, and even more preferably 50 or less. The number of carbon atoms of R ^d is the number including the carbon atoms of these substituents possessed by the alkyl group, the alkenyl group, or the aryl group. For example, 4-(methylthio)benzonitrile is considered to have R ^d as a 4-(methylthio)phenyl group and an aryl group having 7 carbon atoms.

The alkyl group as the substituent is the same as the alkyl group described above, so long as ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. The alkyl group as the substituent has 1 to 11 carbon atoms, preferably 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms.

The alkenyl group as a substituent is the same as the above-mentioned alkenyl group so long as ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. The number of carbon atoms in the alkenyl group as a substituent is 2 to 11, preferably 2 to 6, and more preferably 2 to 3.

The aryl group as a substituent is the same as the above-mentioned aryl group so long as ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. The number of carbon atoms in the aryl group as a substituent is 1 to 11, preferably 3 to 9, and more preferably 5 to 7.

The alkoxy group as a substituent is an alkoxy group having 1 to 11 carbon atoms, preferably an alkoxy group having 1 to 6 carbon atoms, and more preferably an alkoxy group having 1 to 3 carbon atoms, where ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, an s-butoxy group, a t-butoxy group, an n-pentoxy group, an isopentoxy group, and a phenoxy group.

The amino group as a substituent includes an amino group (-NH ₂ ) (number of carbon atoms: 0) having no substituent on the nitrogen atom, and an amino group in which some or all of the hydrogen atoms bonded to the nitrogen atom have been replaced with carbon atoms. The number of carbon atoms in the amino group in which some or all of the hydrogen atoms bonded to the nitrogen atom have been replaced with carbon atoms is 1 to 11, preferably 1 to 6, and more preferably 1 to 3. Here, R ^d is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the amino group include an amino group (-NH ₂ ) having no substituent, a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a dimethylamino group, a diethylamino group, an anilino group, a toluidino group, an anisidino group, and an N-methyl-N-phenylamino group.

Examples of monovalent groups containing a carbonyl group as a substituent include a formyl group, an acyl group, a carboxy group, an amide group, an alkoxycarbonyl group, a thiocarboxy group, and a thioester group.

An acyl group is a substituent in which a carbonyl group is linked to an alkyl group, an alkenyl group, or an aryl group. The total number of carbon atoms (1) derived from the carbonyl group of the acyl group and the number of carbon atoms derived from the alkyl group, the alkenyl group, or the aryl group is 2 to 11, preferably 2 to 7, and more preferably 2 to 4. Here, R ^d is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the acyl group include an acetyl group, a propionyl group, a butylcarbonyl group, a vinylcarbonyl group, and a benzoyl group.

The amide group includes an amide group (-CONH ₂ ) having no substituent on the nitrogen atom, and an amide group in which some or all of the hydrogen atoms bonded to the nitrogen atom are substituted with carbon atoms. The number of carbon atoms in the amide group is 1 to 11, preferably 1 to 7, and more preferably 1 to 4, as the total number of carbon atoms derived from the carbonyl group (1) and the number of carbon atoms substituted on the nitrogen atom. Here, R ^d is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the amide group include an unsubstituted amide group, an N-methylamide group, an N-ethylamide group, an N-phenylamide group, an N,N-dimethylamide group, and an N-methyl-N-phenylamide group.

An alkoxycarbonyl group is a substituent in which a carbonyl group and an alkoxy group are linked, and is also called an ester group. The total number of carbon atoms (1) derived from the carbonyl group and the number of carbon atoms derived from the alkoxy group is 2 to 11, preferably 2 to 7, and more preferably 2 to 4. Here, R ^d is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl group, and a phenoxycarbonyl group.

A thioester group is a substituent in which a carbonyl group is linked to an alkylthio group or an arylthio group. The total number of carbon atoms (1) derived from the carbonyl group and the number of carbon atoms derived from the alkylthio group or the arylthio group is 2 to 11, preferably 2 to 7, and more preferably 2 to 4. Here, R ^d is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of thioester groups include a methylthiocarbonyl group, an ethylthiocarbonyl group, a butylthiocarbonyl group, and a phenylthiocarbonyl group.

The alkylthio group as a substituent is an alkylthio group having 1 to 11 carbon atoms, preferably an alkylthio group having 1 to 6 carbon atoms, and more preferably an alkylthio group having 1 to 3 carbon atoms, where ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, a propylthio group, and an isopropylthio group.

The arylthio group as a substituent is an arylthio group having 1 to 11 carbon atoms, preferably an arylthio group having 3 to 10 carbon atoms, and more preferably an arylthio group having 6 to 10 carbon atoms, where ^Rd is an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an aryl group having 1 to 12 carbon atoms. Examples of the arylthio group include a phenylthio group and a tolylthio group.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, Component A4 is preferably methacrylonitrile, acetonitrile, propionitrile, acrylonitrile, benzonitrile, 3-hydroxypropionitrile, 3-methoxypropionitrile, 4-aminobenzonitrile, 4'-cyanoacetophenone, 4-(methylthio)benzonitrile, 2-hydroxypropionitrile, 2-aminopropionitrile, or 4-cyanophenol, more preferably methacrylonitrile, acetonitrile, propionitrile, acrylonitrile, benzonitrile, 3-hydroxypropionitrile, 3-methoxypropionitrile, 4-aminobenzonitrile, 4'-cyanoacetophenone, or 4-(methylthio)benzonitrile, even more preferably methacrylonitrile, acetonitrile, propionitrile, acrylonitrile, 4-cyanoacetophenone, or 4-(methylthio)benzonitrile, and particularly preferably methacrylonitrile, acetonitrile, propionitrile, acrylonitrile, or 4-cyanoacetophenone.

Component A4 may be one type or two or more types.

(Component B)
The methacrylic acid-containing composition according to the fourth aspect contains a polymerization inhibitor (component B). In this specification, the polymerization inhibitor means a compound having a function of suppressing the polymerization reaction of methacrylic acid. Examples of the polymerization inhibitor include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, the polymerization reaction of methacrylic acid due to a radical polymerization mechanism can be suppressed from proceeding during storage of methacrylic acid. In addition, component B can trap the above-mentioned hydroxyl radicals generated during storage of methacrylic acid. That is, when the methacrylic acid-containing composition contains component B in addition to component A4, the amount of hydroxyl radicals can be reduced by two different mechanisms, that is, the generation of hydroxyl radicals can be suppressed by component A4 and the hydroxyl radicals generated by component B can be removed. Therefore, it is considered that the decrease of component B can be efficiently suppressed.

Among the above, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, and for example, it is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenyl phosphite, and phenothiazine. It is more preferable that component B is a phenolic compound, and for example, it is more preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol. It is particularly preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone and 4-methoxyphenol.

Component B may be one type or two or more types.
When a methacrylic acid-containing composition contains a compound corresponding to both component A4 and component B, the compound is regarded as component B. That is, the methacrylic acid-containing composition must contain a component A4 other than the compound. When two or more compounds corresponding to both component A4 and component B are contained, the compound having the highest molar concentration in the methacrylic acid-containing composition is regarded as component B, and the other compounds are regarded as component A4.

(Concentration of Component A4 and Component B)
When the concentration of component A4 is _M (μmol/L) and the concentration of component B is _M (μmol/ _L ), from the viewpoint of the efficiency of inhibiting the production of methacrylic acid dimer and pyruvic acid, M/ _M is preferably 0.005 to 100, and more preferably 0.05 to 10.

M _A4 is preferably 1 to 40,000 μmol/L. By M _A4 being 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. In addition, by M _A4 being 40,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fourth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A4 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, even more preferably 50 μmol/L or more, even more preferably 60 μmol/L or more, particularly preferably 70 μmol/L or more, and especially preferably 80 μmol/L or more. The upper limit of M _A4 is more preferably 3,000 μmol/L or less, even more preferably 25,000 μmol/L or less, and particularly preferably 20,000 μmol/L or less.

M _B is preferably 1 to 50,000 μmol/L. By having M _B of 1 μmol/L or more, the effect of suppressing the production of methacrylic acid dimers and pyruvic acid can be sufficiently obtained. In addition, by having M _B of 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fourth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1500 μmol/L or more, and even more preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 45,000 μmol/L or less, further preferably 40,000 μmol/L or less, particularly preferably 35,000 μmol/L or less, even more preferably 30,000 μmol/L or less, and most preferably 25,000 μmol/L or less.

(Methacrylic acid concentration)
The concentration of methacrylic acid in the methacrylic acid-containing composition according to the fourth aspect is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fourth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. Furthermore, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, particularly preferably 99.50% or more, and most preferably 99.80% by mass or more.

(Component C)
The methacrylic acid-containing composition according to the fourth aspect may further contain component C, which is another compound, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, diacetyl may be contained as an impurity in methacrylic acid, and from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A4, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A4, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A4, it can be determined that the methacrylic acid-containing composition contains component A4. If a standard specimen of component A4 is not available, it can be determined that the peak is a component A4 peak when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A4 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A4. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying it using the area percentage method, and correcting it using the moisture concentration quantified by a Karl Fischer moisture meter. The concentration of component A4 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition and quantifying it using the internal standard method. If a standard specimen of component A4 cannot be obtained and it cannot be quantified by the internal standard method, any organic compound with a known concentration can be measured by GC-FID measurement under the same conditions as the methacrylic acid-containing composition, and the concentration of component A4 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A4 , _S is the peak area of component A4, S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A4 above.
Furthermore, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water therein can be confirmed by the Karl Fischer method.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the fourth aspect includes a method of adding component A4 and component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A4 and component B may be commercially available products, or products synthesized by a known method may be used. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, component A4 or component B may be added in the middle of the raw material or the production process to produce a methacrylic acid-containing composition. In addition, when component A4 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A4 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the fourth aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100 ° C, and the heating time is preferably 1 to 24 hours. In the present invention, the quality stability during storage of a methacrylic acid-containing composition was evaluated by the amount of polymerization inhibitor reduction confirmed when the methacrylic acid-containing composition was stored at 25 ° C for 21 days.

[Methacrylic acid ester manufacturing method]
The method for producing a methacrylic acid ester according to the fourth aspect includes a step of esterifying the methacrylic acid-containing composition according to the fourth aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the fourth aspect]
The method for producing a methacrylic acid polymer according to the fourth aspect includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the fourth aspect.

The monomer copolymerizable with methacrylic acid may be one type or two or more types. In addition, when component A4 is a monomer copolymerizable with methacrylic acid, component A4 may be used as a monomer copolymerizable with methacrylic acid, or a monomer copolymerizable with methacrylic acid may be used separately from component A4.

[Methacrylic acid-containing composition according to the fifth aspect]
The methacrylic acid-containing composition according to the fifth aspect contains methacrylic acid, a compound (component A5) represented by the following formula (51), and a polymerization inhibitor (component B). The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In the above formula (51), R ^1e and R ^2e each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an alkylthio group, or an arylthio group. ^{R 3e} represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, an alkylthio group, or an arylthio group. R ^1e and R ^2e , R ^2e and R ^3e , and R ^3e and R ^1e may be linked to each other to form a ring. However, the total number of carbon atoms of R ^1e and R ^2e is 2 or more.
In addition, the methacrylic acid-containing composition may contain other compounds (component C) and water as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the fifth aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A5)
The methacrylic acid-containing composition according to the fifth aspect contains a compound (component A5) represented by the formula (51). "α hydrogen" refers to a hydrogen atom bonded to a carbon atom adjacent to a carbonyl group carbon atom. The coexistence of component A5 and component B described below can suppress the decomposition of the polymerization inhibitor. The reason for this is presumed to be as follows.

It is known that methacrylic acid polymerizes due to radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes into another compound when trapping the radicals, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated by oxygen molecules absorbing ultraviolet light derived from sunlight. Component A5 can trap a radical intermediate generated by the reaction of a hydroxyl radical with methacrylic acid and return the intermediate to methacrylic acid. Therefore, the radicals that component B needs to trap are reduced, and the decrease in the concentration of component B can be suppressed.
In addition, when the methacrylic acid composition contains a carboxylic acid such as propionic acid or acrylic acid as an impurity, the concentration of the carboxylic acid decreases during storage. This is presumed to be decomposition due to decarboxylation. Since component A5 is a proton donor, it can donate a proton to the anion intermediate generated by the decarboxylation reaction, and is therefore presumed to promote the decarboxylation reaction.

The molecular weight of component A5 is preferably 1000 or less. By having a molecular weight of 1000 or less, the number of α hydrogens per unit mass in component A5 can be increased, so that the effects of the present invention can be obtained with a small mass. The molecular weight of component A5 is more preferably 800 or less, even more preferably 600 or less, and particularly preferably 400 or less.

R ^1e and R ^2e in the formula (51) each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an alkylthio group, an arylthio group, or an alkylamino group. R ^1e and R ^2e may be the same or different. R ^3e in the formula (51) represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, an alkylthio group, or an arylthio group. R ^3e and R ^1e , and R ^3e and R ^2e may be the same or different. R ^1e and R ^2e , R ^2e and R ^3e , and R ^3e and R ^1e may each be linked to each other to form a ring.

In general, the α hydrogen of component A5 has a property of reacting with anions and radicals, but the reactivity may decrease depending on the type of the substituent. When R ^1e , R ^2e and R ^3e satisfy the above conditions, the reactivity of the α hydrogen of component A5 with anions and radicals is maintained, so that the effect of the present invention can be obtained. R ^1e and R ^2e are preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, an arylthio group having 6 to 10 carbon atoms, or an alkylamino group having 0 to 6 carbon atoms. These are highly stable substituents, so that it is possible to prevent component A5 from changing into other compounds during storage. In addition, because of the low electron donating property, the acidity of the α hydrogen of component A5 is improved. R ^1e and R ^2e are more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, an arylthio group having 6 to 10 carbon atoms, or an alkylamino group having 0 to 6 carbon atoms; more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkylamino group having 0 to 6 carbon atoms; particularly preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkylamino group having 0 to 6 carbon atoms; particularly preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, a hydroxy group, a methoxy group, a cyclohexyl group, or an N,N-dimethylamino group; and most preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a hydroxy group, a methoxy group, a cyclohexyl group, or an N,N-dimethylamino group.

R ^3e is more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms. These are highly stable substituents, so that it is possible to prevent component A5 from changing into other compounds during storage. R ^3e is more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or an amino group having 0 to 6 carbon atoms, and is even more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an amino group having 0 to 6 carbon atoms, or a hydroxy group, and is particularly preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an isopropenyl group, or a hydroxy group, and is most preferably a hydrogen atom, a methyl group, an isopropyl group, or a hydroxy group.

The alkyl group is a chain-like (straight-chain or branched) alkyl group or a cyclic alkyl group. In the case of a chain-like alkyl group, a chain-like alkyl group having 1 to 20 carbon atoms is preferable, a chain-like alkyl group having 1 to 10 carbon atoms is more preferable, and a chain-like alkyl group having 1 to 5 carbon atoms is even more preferable. Examples of the chain-like alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, an t-butyl group, an n-pentyl group, an isopentyl group, a hexyl group, an octyl group, a decyl group, a hydroxymethyl group, a 1-hydroxyethyl group, and a 2-hydroxyethyl group, and the like are included, with a methyl group, an ethyl group, an n-propyl group, and an isopropyl group being preferred. In the case of a cyclic alkyl group, a cyclic alkyl group having 3 to 20 carbon atoms is preferable, a cyclic alkyl group having 4 to 10 carbon atoms is more preferable, and a cyclic alkyl group having 5 to 7 carbon atoms is even more preferable. Examples of the cyclic alkyl group include a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group.

The alkenyl group is a chain (straight-chain or branched) alkenyl group or a cyclic alkenyl group. In the case of a chain alkenyl group, a chain alkenyl group having 2 to 20 carbon atoms is preferred, a chain alkenyl group having 2 to 10 carbon atoms is more preferred, and a chain alkenyl group having 2 to 5 carbon atoms is even more preferred. Examples of the chain alkenyl group include a vinyl group, a 1-propenyl group, an isopropenyl group, a 2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group, and a 2-hexenyl group. In the case of a cyclic alkenyl group, a cyclic alkenyl group having 3 to 20 carbon atoms is preferred, a cyclic alkenyl group having 4 to 10 carbon atoms is more preferred, and a cyclic alkenyl group having 5 to 7 carbon atoms is even more preferred. Examples of the cyclic alkenyl group include a cyclopentenyl group and a cyclohexenyl group.

The alkoxy group is preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 10 carbon atoms, and even more preferably an alkoxy group having 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, butoxy, and phenoxy groups.

R ^1e and R ^2e , R ^2e and R ^3e , and R ^3e and R ^1e may be linked to each other to form a ring. Examples of the compound in which R ^1e and R ^2e are linked to form a ring include cyclohexane carboxylic acid, methyl cyclohexane carboxylate, cyclopentane carboxylic acid, and methyl cyclopentane carboxylate. Examples of the compound in which R ^2e and R ^3e are linked to form a ring, and the compound in which R ^3e and R ^1e are linked to form a ring include 2,5-dimethyl-2-cyclopenten-1-one, 2-methyl-5-isopropyl-1-cyclohexanone, α-methyl-δ-valerolactone, and α-methyl-γ-butyrolactone.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, the following compounds are considered as component A5: isobutyric acid, isovaleric acid, 2-methylbutyric acid, acetonylacetone, 3-methyl-3-buten-2-one, isobutyraldehyde, cyclohexanecarboxylic acid, 2-methoxypropionic acid, N,N-dimethylglycine, malonic acid, methylthioacetic acid, 3-butenoic acid, butyric acid, palmitic acid, stearic acid, methyl isobutyrate, ethyl isobutyrate, isobutyl isobutyrate, isoamyl isobutyrate, phenyl isobutyrate, methyl butyrate, methyl isovalerate, methyl isopropyl ketone, 3-hexen-2-one, 2,5-dimethyl-2-cyclopenten-1-one, 2-methyl-5-isopropyl-1-cyclohexanone, 2-acetylfuran, butyraldehyde, 2-methylbutyraldehyde, 3-methylbutyraldehyde, (R)-(-)-3-hydroxyisobutyric acid, cyclo Pentanecarboxylic acid, α-methyl-δ-valerolactone, or α-methyl-γ-butyrolactone is preferred, and isobutyric acid, isovaleric acid, 2-methylbutyric acid, acetonylacetone, 3-methyl-3-buten-2-one, isobutyraldehyde, cyclohexanecarboxylic acid, 2-methoxypropionic acid, N,N-dimethylglycine, malonic acid, methylthioacetic acid, 3-butenoic acid, and methylisopropenyl ketone are more preferred, and isobutyric acid, isovaleric acid, 2-methylbutyric acid, 2-methoxypropionic acid, N,N-dimethylglycine, acetonylacetone, 3-methyl-3-buten-2-one, isobutyraldehyde, and methylisopropenyl ketone are even more preferred, and isobutyric acid, isovaleric acid, 2-methylbutyric acid, acetonylacetone, isopropenyl methyl ketone, isobutyraldehyde, cyclohexanecarboxylic acid, 2-methoxypropionic acid, and N,N-dimethylglycine are particularly preferred.

Component A5 may be one type or two or more types.

(Component B)
The methacrylic acid-containing composition according to the fifth aspect contains a polymerization inhibitor (component B). In this specification, the polymerization inhibitor means a compound having a function of suppressing the polymerization reaction of methacrylic acid. Examples of the polymerization inhibitor include phenol-based compounds, quinone-based compounds, nitrobenzene-based compounds, N-oxyl-based compounds, amine-based compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, it is possible to suppress the progress of the polymerization reaction of methacrylic acid by a radical polymerization mechanism during storage of methacrylic acid. In addition, as described above, the coexistence of component A5 and component B can efficiently suppress the decrease of component B.

Nitrophenols include, for example, o-nitrophenol, m-nitrophenol, p-nitrophenol, and 2,4-dinitrophenol.

Nitrosophenols include, for example, o-nitrosophenol, m-nitrosophenol, p-nitrosophenol, α-nitroso-β-naphthol, etc.

Among the above, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, it is preferable that component B is at least one polymerization inhibitor selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, and is preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenylphosphite, and phenothiazine. It is more preferable that component B is a phenolic compound, and is more preferably at least one polymerization inhibitor selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol. It is particularly preferable that component B is at least one polymerization inhibitor selected from the group consisting of hydroquinone and 4-methoxyphenol.

Component B may be one type or two or more types.
When a methacrylic acid-containing composition contains a compound corresponding to both component A5 and component B, the compound is regarded as component B. That is, the methacrylic acid-containing composition must contain a component A5 other than the compound. When two or more compounds corresponding to both component A5 and component B are contained, the compound having the highest molar concentration in the methacrylic acid composition is regarded as component B, and the other compounds are regarded as component A5.

(Concentration of Component A5 and Component B)
When the concentration of component A5 is _M (μmol/L) and the concentration of component B is _M (μmol/L), _M / _M is preferably 0.005 to 100. From the viewpoint of the efficiency of inhibiting the production of pyruvic acid, it is more preferable that the lower limit of _M / _M is 0.05 or more and the upper limit is 10 or less.

M _A5 is preferably 1 to 40,000 μmol/L. By M _A5 being 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. In addition, by M _A5 being 40,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fifth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A5 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, even more preferably 50 μmol/L or more, and even more preferably 55 μmol/L or more. The upper limit of M _A3 is more preferably 3,000 μmol/L or less, even more preferably 25,000 μmol/L or less, and particularly preferably 20,000 μmol/L or less.

It is preferable that M _B is 1 to 50,000 μmol/L. By having M _B of 1 μmol/L or more, the effect of suppressing the production of methacrylic acid dimers and pyruvic acid can be sufficiently obtained. In addition, by having M _B of 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fifth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1500 μmol/L or more, and even more preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 45,000 μmol/L or less, further preferably 40,000 μmol/L or less, particularly preferably 35,000 μmol/L or less, even more preferably 30,000 μmol/L or less, and most preferably 25,000 μmol/L or less.

(Methacrylic acid concentration)
The concentration of methacrylic acid in the methacrylic acid-containing composition according to the fifth aspect is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the fifth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. Furthermore, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, particularly preferably 99.50% or more, and most preferably 99.80% by mass or more.

(Component C)
The methacrylic acid-containing composition according to the fifth aspect may further contain component C, which is another compound, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, diacetyl may be contained as an impurity in methacrylic acid, and from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L or less, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A5, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A5, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A5, it can be determined that the methacrylic acid-containing composition contains component A5. If a standard specimen of component A5 is not available, it can be determined that the peak is a component A5 peak when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A5 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A5. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying it using the area percentage method, and correcting it using the moisture concentration quantified by a Karl Fischer moisture meter. The concentration of component A5 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition and quantifying it using the internal standard method. If a standard specimen of component A5 cannot be obtained and cannot be quantified by the internal standard method, GC-FID measurement is performed on any organic compound with a known concentration under the same conditions as the methacrylic acid-containing composition, and the concentration of component A5 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A5 , _S is the peak area of component A5, S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A5 above.
Furthermore, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water therein can be confirmed by the Karl Fischer method.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the fifth aspect includes a method of adding component A5 and component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A5 and component B may be commercially available products, or products synthesized by a known method may be used. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, component A5 or component B may be added in the middle of the raw material or the production process to produce a methacrylic acid-containing composition. In addition, when component A5 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A5 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the fifth aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100 ° C, and the heating time is preferably 1 to 24 hours. In the fifth aspect, the quality stability of the methacrylic acid-containing composition during storage was evaluated by the amount of polymerization inhibitor reduction when the methacrylic acid-containing composition was stored at 25 ° C for 21 days.

[Methacrylic acid ester manufacturing method]
The method for producing a methacrylic acid ester according to the fifth aspect includes a step of esterifying the methacrylic acid-containing composition according to the fifth aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the fifth aspect]
The method for producing a methacrylic acid polymer according to the present invention includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the present invention.

Examples of monomers copolymerizable with methacrylic acid include the following.
Methacrylic acid esters such as ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, or benzyl methacrylate;
acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, or 2-ethylhexyl acrylate;
Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, or itaconic acid;
Unsaturated carboxylic acid anhydrides such as maleic anhydride or itaconic anhydride;
Maleimides such as N-phenylmaleimide or N-cyclohexylmaleimide;
Hydroxy group-containing vinyl monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate;
Vinyl esters such as vinyl acetate or vinyl benzoate;
Vinyl chloride, vinylidene chloride and their derivatives;
Nitrogen-containing vinyl monomers such as methacrylamide or acrylonitrile;
Epoxy group-containing monomers such as glycidyl acrylate or glycidyl methacrylate;
Aromatic vinyl monomers such as styrene or α-methylstyrene;
Alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, or 1,6-hexanediol di(meth)acrylate;
polyoxyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, or neopentyl glycol di(meth)acrylate;
Vinyl monomers having two or more ethylenically unsaturated bonds in the molecule, such as divinylbenzene;
an unsaturated polyester prepolymer obtained from at least one polycarboxylic acid including an ethylenically unsaturated polycarboxylic acid and at least one diol;
A vinyl ester prepolymer obtained by modifying the terminal epoxy group with an acrylic acid.

Among the above, the monomer copolymerizable with methacrylic acid is preferably at least one selected from the group consisting of methacrylic acid esters and acrylic acid esters. The monomer copolymerizable with methacrylic acid is more preferably a methacrylic acid ester, and particularly preferably methyl methacrylate.
The monomer copolymerizable with methacrylic acid may be one type or two or more types.

[Sixth aspect methacrylic acid-containing composition]
The methacrylic acid-containing composition according to the sixth aspect contains methacrylic acid, a compound (component A6) represented by the following formula (61), and a polymerization inhibitor (component B). The concentration of the methacrylic acid is 98.00 to 99.99% by mass.

In formula (61), R ^1f , R ^2f and R ^3f each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, an alkylthio group or an arylthio group. R ^4f represents an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. However, R ^1f = H, R ^2f = H, R ^3f = CH ₃ , and R ^4f = OH, that is, excluding the case where the compound represented by formula (61) is methacrylic acid. H represents a hydrogen atom, C represents a carbon atom, and O represents an oxygen atom.
In addition, the methacrylic acid-containing composition may contain other compounds (component C) and water as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Each item will be described in detail below.

(Methacrylic acid)
The methacrylic acid-containing composition according to the sixth aspect contains methacrylic acid. Methacrylic acid can be produced, for example, as a by-product of the acetone cyanohydrin (ACH) method or as an intermediate of the C4 direct oxidation method. The methacrylic acid contained in the methacrylic acid-containing composition is preferably produced by the C4 direct oxidation method, and more preferably produced by the C4 direct oxidation method using isobutanol derived from biomass as a starting material.

(Component A6)
The methacrylic acid-containing composition according to the sixth aspect contains a compound (component A6) represented by the formula (61). The coexistence of component A6 and component B described later can suppress the decomposition of the polymerization inhibitor during storage of the methacrylic acid-containing composition. In addition, when the methacrylic acid-containing composition contains impurities such as acrylic acid and propionic acid, the decomposition can be promoted to reduce the impurity concentration. The reason for this is presumed to be as follows.

It is known that methacrylic acid is polymerized by radicals generated during storage, and a polymerization inhibitor (component B) is added to prevent polymerization. Component B has a polymerization prevention function by trapping radicals generated during storage of methacrylic acid, but since the polymerization inhibitor decomposes into another compound when trapping the radicals, the concentration of component B in the methacrylic acid-containing composition gradually decreases during storage, and the polymerization prevention function gradually decreases. Furthermore, unnecessary decomposition products generated by component B trapping radicals gradually increase. An example of a radical generated during storage of methacrylic acid is a hydroxyl radical generated by oxygen molecules absorbing ultraviolet light derived from sunlight. Hydroxyl radicals also cause the generation of pyruvic acid due to the oxidation of methacrylic acid. Component A6 absorbs ultraviolet light because it has a conjugated double bond, and the absorption wavelength changes depending on the type of substituent. And component A6 can absorb ultraviolet light of a wide range of wavelengths. Therefore, when the methacrylic acid-containing composition contains component A6, ultraviolet light of a wide range of wavelengths is absorbed, and the generation of hydroxyl radicals is suppressed. Therefore, the number of radicals that component B needs to trap is reduced, and the decrease in the concentration of component B can be suppressed.
Among various organic compounds that absorb ultraviolet light, component A6 has a molecular structure similar to that of methacrylic acid, and therefore when the methacrylic acid-containing composition is used as a raw material to produce a polymer, the adverse effects of containing component A6 as an impurity can be reduced.

The molecular weight of component A6 is preferably 1000 or less. By having a molecular weight of 1000 or less, the number of conjugated double bonds per unit mass in component A6 can be increased, so that the effects of the present invention can be obtained with a small mass. The molecular weight of component A6 is more preferably 800 or less, even more preferably 600 or less, and particularly preferably 400 or less.

R ^1f , R ^2f and R ^3f in the formula (61) each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, an alkylthio group or an arylthio group. R ^4f in the formula (61) represents an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group or an arylthio group. R ^1f , R ^2f , R ^3f and R ^4f may be the same or different.

When R ^1f _, R ^2f _, R ^3f and R ^4f satisfy the above conditions, the π-conjugated system of component A6 is maintained, so that it has the property of absorbing ultraviolet light of a wide wavelength, and the effects of the present invention can be obtained. R ^1f , R ^2f and R ^3f are preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms or an arylthio group having 6 to 10 carbon atoms. These are highly stable substituents, so that component A6 can be prevented from changing into other compounds during storage. In addition, when component A6 has these substituents, one molecule of component A6 can absorb a sufficient amount of ultraviolet light. R ^1f , R ^2f and R ^3f are more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an aryl group having 6 to 12 carbon atoms, still more preferably a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and at least one of them is an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 12 carbon atoms, and particularly preferably a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group, or a phenyl group, and at least one of them is a methyl group, an ethyl group, an n-propyl group or an isopropyl group, or a phenyl group, and particularly preferably a hydrogen atom, a methyl group, an ethyl group, an isopropyl group, or a phenyl group, and at least one of them is a methyl group, an ethyl group, an isopropyl group, or a phenyl group.

In addition, R ^4f is preferably an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms. These are highly stable substituents, so that it is possible to prevent component A6 from changing into other compounds during storage. R ^4f is more preferably an alkyl group having 1 to 5 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or an amino group having 0 to 6 carbon atoms, and is particularly preferably a methyl group, an ethyl group, an n-propyl group or an isopropyl group, a hydroxy group, a methoxy group, or an amino group, and is particularly preferably a methyl group, a hydroxy group, a methoxy group, or an amino group. When R ^4f has this structure, the quality stability of the methacrylic acid-containing composition during storage can be improved.

Among the compounds that satisfy the above conditions, from the viewpoint of the quality stability during storage of the methacrylic acid-containing composition, the following compounds are considered as component A6: crotonic acid, 2-methylcrotonic acid, 3,3-dimethylacrylic acid, 2-methylene-3-butenoic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, methyl methacrylate, methyl acrylate, 3-methyl-3-buten-2-one (isopropenyl methyl ketone), N-propyl methacrylic acid, , cinnamic acid, 3-methoxyacrylic acid, cis-crotonic acid, 2-ethylacrylic acid, 2-methylenepentanoic acid, 4-methyl-2-pentenoic acid, 2,4-pentadienoic acid, 2-methyl-2,4-pentadienoic acid, 2-hexenoic acid, 2-methyl-2-hexenoic acid, 2-methylenehexanoic acid, 2-heptenoic acid, 2,4-heptadienoic acid, 2-octenoic acid, 2,4-octadienoic acid, 2,6-dimethyl-2-heptenoic acid, 6-Methyl-2-methyleneheptanoic acid, 2,6-dimethyl-2,4-heptadienoic acid, 6-methyl-2-methylene-3-heptenoic acid, 2,5-dimethyl-2,4-hexadienedioic acid, ethyl methacrylate, isobutyl methacrylate, butyl methacrylate, propyl methacrylate, isoamyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, hexyl methacrylate, propyl acrylate, a Butyl acrylate, methyl crotonate, cis-methyl crotonate, methyl 3,3-dimethylacrylate, methyl 2-ethylacrylate, methyl 2-methylene-3-butenoate, methyl 2-pentenoate, methyl 2,4-pentadienoate, dimethyl fumarate, trans-3-hexen-2-one, methyl vinyl ketone, acrolein, crotonaldehyde, cis-crotonaldehyde, 2-methylene-3-butanal, 3,3-Dimethylacrolein, 2-ethylacrolein, 2,4-pentadienal, 2-pentenal, 2-methyl-2,4-pentadienal, 4-methyl-2-pentenal, 2-methyl-2-pentenal, 2-methylenepentanal, 2-hexanal, 2-methyl-2-hexenal, 2-methylenehexanal, 2-heptanal, 2,4-heptadienal, 2-octenal, 2,4-octadecane Dienal, 2,6-dimethyl-2-heptenal, 6-methyl-2-methyleneheptanal, 2,6-dimethyl-2,4-heptadienal, 6-methyl-2-methylene-3-heptenal, 2,5-dimethyl-2,4-hexadienedial, methacrylamide, hexadecanamide, 9-octadecenamide, or methacrylic anhydride is preferred, and crotonic acid, 2-methylcrotonic acid, 3,3-dimethylacrylamide, 2-methyl-2-methyl-3 ... Acid, 2-methylene-3-butenoic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, methyl methacrylate, methyl acrylate, 3-methyl-3-buten-2-one (isopropenyl methyl ketone), N-propyl methacrylamide, cinnamic acid, or 3-methoxyacrylic acid is more preferred, crotonic acid, 2-methyl crotonic acid, 3,3-dimethylacrylic acid, 2-methylene-3-butenoic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, methyl acrylate, 3-methyl-3-buten-2-one (isopropenyl methyl ketone), N-propyl methacrylamide, methacrylamide, and cinnamic acid are even more preferred, and crotonic acid, 2-methyl crotonic acid, 3,3-dimethylacrylic acid, 2-pentenoic acid, 2-methyl-2-pentenoic acid, methyl acrylate, isopropenyl methyl ketone, methacrylamide, and cinnamic acid are particularly preferred.

Component A6 may be one type or two or more types.

(Component B)
The methacrylic acid-containing composition according to the sixth aspect contains a polymerization inhibitor (component B). In this specification, the polymerization inhibitor means a compound having a function of suppressing the polymerization reaction of methacrylic acid. Examples of the polymerization inhibitor include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. By containing component B, the polymerization reaction of methacrylic acid due to a radical polymerization mechanism can be suppressed from proceeding during storage of methacrylic acid. In addition, component B can trap the above-mentioned hydroxyl radicals generated during storage of methacrylic acid. That is, when the methacrylic acid-containing composition contains component B in addition to component A6, the amount of hydroxyl radicals can be reduced by two different mechanisms, that is, the generation of hydroxyl radicals can be suppressed by component A6 and the hydroxyl radicals generated by component B can be removed. Therefore, it is considered that the decrease of component B can be efficiently suppressed.

Component B may be one type or two or more types.
When a methacrylic acid-containing composition contains a compound corresponding to both component A6 and component B, the compound is regarded as component B. That is, the methacrylic acid-containing composition must contain a component A6 other than the compound. When two or more compounds corresponding to both component A6 and component B are contained, the compound having the highest molar concentration in the methacrylic acid-containing composition is regarded as component B, and the other compounds are regarded as component A6.

(Concentration of Component A6 and Component B)
When the concentration of component _A6 is M (μmol/L) and the concentration of component B is _M (μmol/ _L ), from the viewpoint of efficiency in suppressing consumption of the polymerization inhibitor, _M /M is preferably 0.0005 to 500, more preferably 0.001 to 450, even more preferably 0.005 to 400, and even more preferably 0.005 to 350.

M _A6 is preferably 1 to 85,000 μmol/L. When M _A6 is 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. Furthermore, when M _A6 is 85,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the sixth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _A6 is more preferably 10 μmol/L or more, even more preferably 30 μmol/L or more, more preferably 50 μmol/L or more, particularly preferably 70 μmol/L or more, particularly preferably 80 μmol/L or more, and most preferably 85 μmol/L or more. The upper limit of M _A6 is more preferably 65,000 μmol/L or less, further preferably 45,000 μmol/L or less, particularly preferably 25,000 μmol/L or less, even more preferably 15,000 μmol/L or less, and most preferably 5,000 μmol/L or less.

M _B is preferably 1 to 50,000 μmol/L. By having M _B of 1 μmol/L or more, the effect of suppressing the decomposition of the polymerization inhibitor can be sufficiently obtained. Furthermore, by having M _B of 50,000 μmol/L or less, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition according to the sixth aspect can be reduced, and adverse effects on the physical properties of the polymer can be prevented. The lower limit of M _B is more preferably 10 μmol/L or more, even more preferably 100 μmol/L or more, particularly preferably 1000 μmol/L or more, and especially preferably 2000 μmol/L or more. The upper limit of M _B is more preferably 40,000 μmol/L or less, even more preferably 30,000 μmol/L or less, and particularly preferably 25,000 μmol/L or less.

(Methacrylic acid concentration)
The concentration of methacrylic acid in the methacrylic acid-containing composition according to the sixth aspect is 98.00 to 99.99% by mass. By having a concentration of methacrylic acid of 98.00% by mass or more, the amount of impurities when a methacrylic acid polymer is produced by polymerization of the methacrylic acid-containing composition can be reduced, and adverse effects on the physical properties of the polymer can be prevented. Furthermore, by having a concentration of methacrylic acid of 99.99% by mass or less, purification costs can be reduced. The lower limit of the concentration of methacrylic acid is more preferably 98.50% or more, even more preferably 99.00% or more, particularly preferably 99.50% or more, and most preferably 99.80% by mass or more.

(Component C)
The methacrylic acid-containing composition according to the sixth aspect may further contain component C, which is another compound, as long as the concentration of methacrylic acid satisfies 98.00 to 99.99% by mass. Examples of component C include impurities generated during the production of methacrylic acid. For example, diacetyl may be contained as an impurity in methacrylic acid, and from the viewpoint of reducing coloration of the methacrylic acid-containing composition, the concentration of diacetyl is preferably 55 μmol/L or less, more preferably 20 μmol/L or less, even more preferably 10 μmol/L or less, and particularly preferably 1 μmol/L or less.

(Analysis of methacrylic acid-containing composition)
It can be confirmed, for example, by GC-MS measurement that the methacrylic acid-containing composition contains component A6, component B, component C, and water. In the GC-MS chart of the methacrylic acid-containing composition, if a peak is present at the same retention time as a standard specimen of component A6, and the m / z value detected in the mass spectrum of the peak matches the exact mass of component A6, it can be determined that the methacrylic acid-containing composition contains component A6. If a standard specimen of component A6 is not available, it can be determined that the peak is a component A6 peak when the mass spectrum pattern of the peak appearing in the GC-MS chart of the methacrylic acid-containing composition matches the mass spectrum pattern of component A6 recorded in the mass spectrum database. That is, it can be determined that the methacrylic acid-containing composition contains component A6. Examples of mass spectrum databases include NIST20, NIST17, NIST14, NIST14s, and the like. In addition, when the volatility is low and detection by GC-MS measurement is not possible, it can be detected using LC-MS. The presence of components B, C and water can also be confirmed by the same method.
The concentration of methacrylic acid can be calculated, for example, by performing GC-FID measurement of the methacrylic acid-containing composition, quantifying it using the area percentage method, and correcting it using the moisture concentration quantified by a Karl Fischer moisture meter. The concentration of component A6 can be calculated, for example, by performing GC measurement of the methacrylic acid-containing composition and quantifying it using the internal standard method. If a standard specimen of component A6 cannot be obtained and cannot be quantified by the internal standard method, GC-FID measurement is performed on any organic compound with a known concentration under the same conditions as the methacrylic acid-containing composition, and the concentration of component A6 can be calculated using the following formula.

Here, N is the number of carbon atoms in one molecule of the organic compound of known concentration, N is the number of carbon atoms in one molecule of component _A6 , _S is the peak area of component A6, S is the peak area of the organic compound of known concentration, and M is the concentration (μmol/L) of the organic compound of known concentration.

When the volatility is low and quantitative determination by GC measurement is not possible, quantitative determination can be performed using a chromatographic method such as LC.
The concentrations of components B and C can be calculated in the same manner as for component A6.
Furthermore, the presence or absence of water in the methacrylic acid-containing composition and the concentration of water therein can be confirmed by the Karl Fischer method.

[Methacrylic acid-containing composition production method]
The method for producing the methacrylic acid-containing composition according to the sixth aspect includes a method of adding component A6 and component B to methacrylic acid. Methacrylic acid may be a commercially available product, or methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method. Component A6 and component B may be commercially available products, or products synthesized by a known method may be used. When methacrylic acid produced by a known method such as the acetone cyanohydrin (ACH) method or the C4 direct oxidation method is used, component A6 or component B may be added in the middle of the raw material or the production process to produce a methacrylic acid-containing composition. In addition, when component A6 or component B is produced as a by-product in the methacrylic acid production process, a methacrylic acid-containing composition may be produced by leaving a part of the produced component A6 or component B.

[Evaluation method for storage stability and thermal stability]
The methacrylic acid-containing composition according to the sixth aspect has high quality stability during storage. As a method for evaluating the quality stability during storage of a methacrylic acid-containing composition, for example, a method of actually storing a methacrylic acid-containing composition for a long period of time and confirming the amount of polymerization inhibitor reduction can be mentioned. In addition, from the viewpoint of ease of operation, a method of heating a methacrylic acid-containing composition for a short period of time and confirming the amount of polymerization inhibitor reduction may be used. When heating for a short period of time, the heating temperature is preferably 50 to 100°C, and the heating time is preferably 1 to 24 hours. In the present invention, the quality stability of a methacrylic acid-containing composition during storage was evaluated by the amount of polymerization inhibitor reduction when the methacrylic acid-containing composition was stored at 25°C for 21 days.

[Methacrylic acid ester manufacturing method]
The method for producing a methacrylic acid ester according to the sixth aspect includes a step of esterifying the methacrylic acid-containing composition according to the sixth aspect.
The alcohol to be reacted with the methacrylic acid-containing composition is not particularly limited, and examples thereof include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. Examples of the methacrylic acid ester obtained include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, and isobutyl methacrylate. The esterification reaction can be carried out in the presence of an acid catalyst such as a sulfonic acid type cation exchange resin. The temperature during the esterification reaction is preferably 50 to 200°C.
The pressure during the esterification reaction, the position of the catalyst in the reactor, the proportion of the catalyst in the reactor, etc. are not particularly limited, and any commonly used form can be applied.

[Method for producing methacrylic acid polymer according to the sixth aspect]
The method for producing a methacrylic acid polymer according to the sixth aspect includes a step of polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to the sixth aspect.

The monomer copolymerizable with methacrylic acid may be one type or two or more types. In addition, when component A6 is a monomer copolymerizable with methacrylic acid, component A6 may be used as a monomer copolymerizable with methacrylic acid, or a monomer copolymerizable with methacrylic acid may be used separately from component A6.

In the polymerizable composition, the upper limit of the content of the monomer copolymerizable with methacrylic acid is preferably 99.99 parts by mass or less per 100 parts by mass of the polymerizable composition. The lower limit of the content of the monomer copolymerizable with methacrylic acid is preferably 50 parts by mass or more per 100 parts by mass of the polymerizable composition, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, particularly preferably 80 parts by mass or more, and most preferably 90 parts by mass or more. The upper limit of the content of the monomer copolymerizable with methacrylic acid is more preferably 99.9 parts by mass or less per 100 parts by mass of the polymerizable composition, and even more preferably 99 parts by mass or less.

Hereinafter, the embodiments will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" and "ppm" mean "% by weight" and "ppm by weight" unless otherwise specified.
The water concentration in the reagent methacrylic acid is calculated by the Karl Fischer method. The composition of the components of the methacrylic acid-containing composition before storage was calculated from the amount of each raw material added. The amount of the polymerization inhibitor after storage was quantified by the absolute calibration curve method using GC-FID. The measurement conditions for GC-FID are shown below.
Apparatus: GC-FID (product name: GC7890B, manufactured by Agilent)

[GC conditions]
Column (product name: Rtx-1701, manufactured by Restek)
Length: 30 m, inner diameter: 0.25 mm, membrane thickness: 1.00 μm
Injection volume: 1.0 μL
Vaporization chamber temperature: 260°C
Column oven temperature: held at 40° C. for 10 minutes, heated from 40° C. to 2400° C. at 10° C./min, held at 240° C. for 10 minutes.
Carrier gas: Helium Injection mode: Split (split ratio 50)
Control mode: constant linear velocity (39.723 cm/sec)
Detector temperature: 260°C
Detector H2 flow rate: 30 mL/min
Detector air flow rate: 400 mL/min
Make-up He flow rate: 25 mL/min

The moisture concentration was quantified using the Karl Fischer method using an automatic moisture analyzer (product name: AQV-2200, manufactured by Hiranuma Sangyo Co., Ltd.).

(Example a1)
Using 2-isopropylhydroquinone as a reagent as component A1, 0.0192 g of component A1 was added to 10.0081 g of methacrylic acid as a reagent (containing 366 ppm water concentration and 306 ppm 4-methoxyphenol as component B1) to prepare a methacrylic acid solution (A-a1 solution). The concentration of component A1 in the A-a1 solution is shown in Table 1.
Next, 0.0526 g of A-a1 solution was added to 9.9585 g of methacrylic acid (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm as component B1) as a reagent to prepare a methacrylic acid-containing composition. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 2.
The obtained methacrylic acid-containing composition was stored for 21 days at 25° C. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 2.

(Examples a2, a3, and a5)
Except for using the compound shown in Table 1 as component A and changing the amounts of reagent MAA and component A as shown in Table 1, each Aa solution was prepared in the same manner as in Example a1.
Next, the MAA-containing compositions were prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and the A-a solution were changed as shown in Table 2. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 2.

(Example a4)
An A-a4 solution was prepared in the same manner as in Example a1, except that 2-phenylisobutyric acid was used as the reagent for component A.
Next, using hydroquinone as component B2, 0.4323 g of component B2 was added to 40.0050 g of reagent methacrylic acid (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm as component B1) to prepare a methacrylic acid solution (B-a4). The concentration of component B2 in the B-a4 solution is shown in Table 1.
Next, 0.0600 g of A-a4 solution and 0.2507 g of B-a4 solution were added to 9.7103 g of methacrylic acid (water concentration 366 ppm, 4-methoxyphenol concentration as component B1 306 ppm) as a reagent to prepare a methacrylic acid-containing composition. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 2. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after storage is shown in Table 2.

(Example a6)
Using 2-phenylisobutyric acid as a reagent as component A1, 0.0089 g of component A1 was added to 9.9955 g of methacrylic acid as a reagent (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm as component B1) to prepare a methacrylic acid-containing composition. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 2.

(Examples a7 and a8)
Except for using the compound shown in Table 1 as component A and changing the amounts of reagent MAA and component A as shown in Table 1, each Aa solution was prepared in the same manner as in Example a1.
Except for using the compound shown in Table 1 as component B and changing the amounts of reagent MAA and component B as shown in Table 1, solutions Bb were prepared in the same manner as in Example a4.
Next, MAA-containing compositions were prepared in the same manner as in Example a4, except that the amounts of the reagent MAA, A-a solution, and B-b solution were changed as shown in Table 2. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 2.

(Comparative Example a1)
Using 4-methoxyphenol as a reagent as component B1, 0.4016 g of 4-methoxyphenol was added to 40.0219 g of methacrylic acid as a reagent (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm as component B1) to prepare ratio A-b1.
Next, 0.5000 g of Ba1 solution was added to 19.5000 g of methacrylic acid (water concentration 366 ppm) as a reagent to prepare a methacrylic acid-containing composition. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 2.
The obtained methacrylic acid-containing composition was stored in the same manner as in Example a1. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 2.

(Comparative Example a2)
Reagent methacrylic acid (water concentration: 366 ppm, 4-methoxyphenol concentration as component B1: 306 ppm) was stored for 21 days at 25° C. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 2.

(Comparative Example a3)
A solution Aa was prepared in the same manner as in Example a1, except that the compound shown in Table 1 was used as component A and the amounts of reagent MAA and component A were changed as shown in Table 1.
A methacrylic acid-containing composition was prepared by adding 0.0971 g of A-a solution and 0.0565 g of pure water to 19.4088 g of methacrylic acid (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm) as a reagent. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 2. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after storage is shown in Table 2.

As shown in Tables 1 and 2, in Examples a1 to a8, the rate of decrease in the polymerization inhibitor (component B1) in the methacrylic acid composition after storage was suppressed. This indicates that the quality stability during storage is high.

(Examples b1-b9)
A Ca solution was prepared in the same manner as in Example a1, except that the compound shown in Table 3 was used as Component A21 and the amounts of Reagent MAA and Component A21 were changed as shown in Table 3.
Next, an MAA-containing composition was prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and Ca solution were changed as shown in Table 4. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 4. Table 4 shows the reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days.

(Comparative Example b1)
A methacrylic acid-containing composition was prepared by adding 0.4611 g of Component A21 to 19.5520 g of methacrylic acid (water concentration 366 ppm, 4-methoxyphenol concentration 306 ppm as Component B1) using 2,3,5,6-tetramethylpyrazine as a reagent as Component A21. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 4. The reduction rate of the polymerization inhibitor (Component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 4.

As shown in Tables 3 and 4, in Examples b1 to b9, the decomposition of the polymerization inhibitor (component B1) was suppressed in the methacrylic acid composition after storage. This indicates that the quality stability during storage is high.

(Examples c1, c2, c3, and c5)
Solutions Ca were prepared in the same manner as in Example a1, except that the compound shown in Table 5 was used as component A3 and the amounts of reagent MAA and component A3 were changed as shown in Table 5.
Next, each MAA-containing composition was prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and Ca solution were changed as shown in Table 6. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

(Example c4)
An MAA-containing composition was prepared in the same manner as in Example a4, except that the reagent t-butyl phenyl ether was used for component A3. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

(Example c6)
An MAA-containing composition was prepared in the same manner as in Example a6, except that the reagent t-butyl phenyl ether was used for component A3. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

(Examples c7 and c8)
Solution Ca was prepared in the same manner as in Example a1, except that t-butyl phenyl ether was used as component A3. Solution Cb was then prepared in the same manner as in Example a7.
Methacrylic acid-containing compositions were prepared by adding the reagent MAA, solution Ca, and solution Cb in the amounts shown in Table 6. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

(Comparative Example c1)
A methacrylic acid-containing composition was prepared in the same manner as in Comparative Example b1, except that t-butyl phenyl ether was used as component A. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

(Comparative Example c2)
A methacrylic acid-containing composition was prepared in the same manner as in Comparative Example a3, except that t-butyl phenyl ether was used as component A3. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 6. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 6.

As shown in Tables 5 and 6, in Examples c1 to c8, the decomposition of the polymerization inhibitor (component B1) was suppressed in the methacrylic acid composition after storage. This indicates that the quality stability during storage is high.

(Examples d1 to d6)
Except for using the compound shown in Table 7 as Component A4 and changing the amounts of Reagent MAA and Component A4 as shown in Table 7, each of Solutions Da was prepared in the same manner as in Example a1.
Next, each MAA-containing composition was prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and the Da solution were changed as shown in Table 8. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 8.

(Example d7)
A methacrylic acid-containing composition was prepared in the same manner as in Example a4, except that methacrylonitrile was used as component A4. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 8.

(Example d8)
A solution Da was prepared in the same manner as in Example a1, except that the compound shown in Table 7 was used as Component A4 and the amounts of Reagent MAA and Component A4 were changed as shown in Table 7.
Next, an MAA-containing composition was prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and the Da solution were changed as shown in the table. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 8.

(Example d9)
A methacrylic acid-containing composition was prepared in the same manner as in Example a6, except that methacrylonitrile was used as component A4. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 8.

(Examples d10 and d11)
Except for using methacrylonitrile as component A4, each of the Da solutions was prepared in the same manner as in Example a1. Next, each of the Db solutions was prepared in the same manner as in Example a7.
A methacrylic acid-containing composition was prepared by adding the amounts of reagent MAA, D-a solution, and D-b solution as shown in Table 8. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 8.

(Comparative Example d1)
A methacrylic acid-containing composition was prepared in the same manner as in Comparative Example b1, except that methacrylonitrile was used as component B. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8.
The obtained methacrylic acid-containing composition was stored in the same manner as in Example d1. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition after the storage is shown in Table 8.

(Comparative Example d2)
A methacrylic acid-containing composition was prepared in the same manner as in Comparative Example a1, except that methacrylonitrile was used as component B. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 8. Table 8 shows the reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days.

As shown in Tables 7 and 8, in Examples d1 to d11, the decomposition of the polymerization inhibitor (component B1) was suppressed in the methacrylic acid composition after storage. This indicates that the quality stability during storage is high.

(Examples e1-e9)
A solution Ea was prepared in the same manner as in Example a1, except that the compound shown in Table 9 was used as Component A5 and the amounts of Reagent MAA and Component A5 were changed as shown in Table 9.
Next, an MAA-containing composition was prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and E-a solution were changed as shown in the table. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 10. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 10.

(Example e10)
A methacrylic acid-containing composition was prepared in the same manner as in Example a4, except that isobutyric acid was used as component A5. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 10. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 10.

(Example e11)
A methacrylic acid-containing composition was prepared in the same manner as in Example a6, except that isobutyric acid was used as component A5. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 10. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 10.

(Example e12)
A methacrylic acid-containing composition was prepared in the same manner as in Example a7, except that isobutyric acid was used as component A5. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 10. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days is shown in Table 10.

(Comparative Example e1)
A methacrylic acid-containing composition was prepared in the same manner as in Comparative Example b1, except that isobutyric acid was used as component A5. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 10. Table 10 shows the reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25 ° C for 21 days.

As shown in Tables 9 and 10, in Examples e1 to e12, the decomposition of the polymerization inhibitor (component B1) was suppressed in the methacrylic acid composition after storage. This indicates that the quality stability during storage is high.

(Examples f1 to f10)
Except for using the compound shown in Table 11 as Component A6 and changing the amounts of Reagent MAA and Component A6 as shown in Table 11, each F-a solution was prepared in the same manner as in Example a1.
Next, MAA-containing compositions were prepared in the same manner as in Example a1, except that the amounts of the reagent MAA and the F-a solution were changed as shown in the table. The concentrations of each component in the methacrylic acid-containing composition are shown in Table 12. The reduction rate of the polymerization inhibitor (component B1) in the methacrylic acid-containing composition stored at 25°C for 21 days is shown in Table 12.

As shown in Tables 11 and 12, in Examples f1 to f10, the decomposition of the polymerization inhibitor (component B1) was suppressed in the methacrylic acid composition after storage. This indicates that the quality stability during storage is high.

Methacrylic acid esters can be obtained by esterifying the methacrylic acid-containing composition obtained in this example. Furthermore, methacrylic acid polymers can be obtained by polymerizing a polymerizable composition containing the methacrylic acid-containing composition obtained in this example.

According to the present invention, it is possible to provide a methacrylic acid-containing composition having high quality stability in which decomposition of a polymerization inhibitor during storage is suppressed.
INDUSTRIAL APPLICABILITY According to the present invention, a methacrylic acid-containing composition that can be used as a raw material for acrylic resins, etc. can be stably stored for a long period of time, which is industrially useful.

Claims

Methacrylic acid,
at least one selected from the group consisting of component A1 which is a compound represented by formula (11) below, component A21 which is a compound represented by formula (21) below, component A3 which is a compound represented by formula (31) below, component A4 which is a compound represented by formula (41) below, component A5 which is a compound represented by formula (51) below, and component A6 which is a compound represented by formula (61) below;
Contains
Furthermore, it optionally contains component B, which is a polymerization inhibitor, as necessary,
A methacrylic acid-containing composition having a concentration of methacrylic acid of 98.00 to 99.99% by mass.

In formula (11),
R 1a , R 2a , R 3a , R 4a , R 5a , and R 6a each independently represent a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group containing a carbonyl group, an alkylthio group, or an arylthio group;
two or more of R 1a , R 2a , R 3a , R 4a and R 5a are groups other than a hydrogen atom;
R 7a represents a hydrogen atom, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group, or an arylthio group.

In formula (21),
R 1b , R 2b , R 3b and R 4b each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group or an arylthio group.

In formula (31),
R1c , R2c , R3c , R4c , R5c , R6c , and R7c independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, a monovalent group including a carbonyl group, an alkylthio group, or an arylthio group.

In formula (41),
Rd represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an aryl group having 1 to 12 carbon atoms, and these groups may further have a substituent.

In formula (51),
R 1e and R 2e each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an alkylthio group, or an arylthio group;
R 3e represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group, an alkylthio group, or an arylthio group;
R 1e and R 2e , R 2e and R 3e , and R 3e and R 1e may be linked to each other to form a ring.
However, the total number of carbon atoms of R 1e and R 2e is 2 or more.

In formula (61),
R 1f , R 2f and R 3f each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, an amino group, an alkylthio group or an arylthio group;
R 4f represents a monovalent group including an alkyl group, an alkenyl group, an aryl group, a hydroxy group, an alkoxy group, an amino group or a carbonyl group, an alkylthio group or an arylthio group.
However, this does not include the case where R 1f = H, R 2f = H, R 3f = CH 3 , and R 4f = OH, i.e., the case where the component A6 is methacrylic acid. H represents a hydrogen atom, C represents a carbon atom, and O represents an oxygen atom. The total number of carbon atoms in R 1f , R 2f , and R 3f is 1 or more.
The methacrylic acid-containing composition according to claim 1, wherein M B /M A1 is 0.005 to 100, where M A1 (μmol/L) is the concentration of the component A1 and M B (μmol/L) is the concentration of the component B.
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A1 is M A1 (μmol/L), and M A1 is 1 to 50,000 μmol/L.
The methacrylic acid-containing composition according to claim 3, wherein the M A1 is 10 to 30,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein M B /M A21 is 0.005 to 100, where M A21 is the concentration of the component A21 (μmol/L) and M B is the concentration of the component B (μmol/L).
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A21 is M A21 (μmol/L), and M A21 is 1 to 50,000 μmol/L.
The methacrylic acid-containing composition according to claim 6, wherein the M A21 is 10 to 30,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A3 is M A3 (μmol/L), and M A3 is 1 to 50,000 μmol/L.
The methacrylic acid-containing composition according to claim 8, wherein the M A3 is 10 to 30,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein M B /M A3 is 0.005 to 100, where M A3 is the concentration of the component A3 (μmol/L) and M B is the concentration of the component B (μmol/L).
The methacrylic acid-containing composition according to claim 1, wherein M B /M A4 is 0.005 to 100, where M A4 is the concentration of the component A4 (μmol/L) and M B is the concentration of the component B (μmol/L).
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A4 is M A4 (μmol/L), and M A4 is 1 to 20,000 μmol/L.
The methacrylic acid-containing composition according to claim 12, wherein the M A4 is 10 to 15,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein M B /M A5 is 0.005 to 100, where M A5 is the concentration of the component A5 (μmol/L) and M B is the concentration of the component B (μmol/L).
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A5 is M A5 (μmol/L), and M A5 is 1 to 50,000 μmol/L.
The methacrylic acid-containing composition according to claim 15, wherein the M A5 is 10 to 30,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein M B /M A6 is 0.005 to 100, where M A6 is the concentration of the component A6 (μmol/L) and M B is the concentration of the component B (μmol/L).
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component A is M A6 (μmol/L), and M A6 is 1 to 85,000 μmol/L.
The methacrylic acid-containing composition according to claim 18, wherein the M A6 is 10 to 40,000 μmol / L.
The methacrylic acid-containing composition according to claim 1, wherein the concentration of the component B is M B (μmol/L), and M B is 1 to 50,000 μmol/L.
The methacrylic acid-containing composition according to claim 20, wherein the M B is 10 to 10,000 μmol / L.
In formula (11),
R 1a , R 2a , R 3a , R 4a , R 5a and R 6a each independently represent a monovalent group containing a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a carbonyl group having 1 to 6 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 7a is a monovalent group containing a hydrogen atom, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a carbonyl group having 1 to 6 carbon atoms.
In formula (11),
R 1a , R 2a , R 3a , R 4a , R 5a and R 6a each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group or an alkoxy group having 1 to 6 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 7a is a hydrogen atom, a carboxy group, or an alkoxycarbonyl group having 2 to 6 carbon atoms.
In formula (11),
R 1a , R 2a , R 3a , R 4a , R 5a and R 6a each independently represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an i-butyl group, a t-butyl group, a hydroxy group or a methoxy group;
The methacrylic acid-containing composition according to claim 1 , wherein R 7a is a hydrogen atom, a carboxy group, or a methoxycarbonyl group.
In formula (21),
The methacrylic acid-containing composition according to claim 1, wherein R 1b , R 2b , R 3b and R 4b are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms.
In formula (21),
The methacrylic acid-containing composition according to claim 1, wherein R 1b , R 2b , R 3b and R 4b are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.
In formula (21),
The methacrylic acid-containing composition according to claim 1, wherein R 1b , R 2b , R 3b and R 4b are each independently a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, or a methoxy group.
In formula (31),
The methacrylic acid-containing composition according to claim 1, wherein R 1c , R 2c , R 3c , R 4c , R 5c , R 6c and R 7c are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, or a monovalent group containing a carbonyl group having 1 to 6 carbon atoms.
In formula (31),
The methacrylic acid-containing composition according to claim 1, wherein R 1c , R 2c , R 3c , R 4c , R 5c , R 6c and R 7c are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, an alkoxy group having 1 to 5 carbon atoms, a carboxy group or an alkoxycarbonyl group having 2 to 6 carbon atoms.
In formula (31),
The methacrylic acid-containing composition according to claim 1, wherein R 1c , R 2c , R 3c , R 4c , R 5c , R 6c and R 7c are each independently a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an i-butyl group, a t-butyl group, a hydroxy group, a methoxy group, a carboxy group or a methoxycarbonyl group.
In formula (41),
The methacrylic acid-containing composition according to claim 1, wherein R d is an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, or an aryl group having 6 to 8 carbon atoms.
In formula (41),
The methacrylic acid-containing composition according to claim 1 , wherein R d is a methyl group, an ethyl group, a vinyl group, an isopropenyl group, or a phenyl group.
In formula (51),
R 1e and R 2e each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 3e is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms.
In formula (51),
R 1e and R 2e are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 3e is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 6 carbon atoms.
In formula (51),
R 1e and R 2e each independently represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or an isopropyl group;
The methacrylic acid-containing composition of claim 1 , wherein R 3e is a hydroxy group.
In formula (61),
R 1f , R 2f and R 3f each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 4f is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 1 to 12 carbon atoms, a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, an amino group having 0 to 6 carbon atoms, a monovalent group containing a carbonyl group having 1 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, or an arylthio group having 6 to 10 carbon atoms.
In formula (61),
R 1f , R 2f and R 3f each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms;
The methacrylic acid-containing composition according to claim 1, wherein R 4f is an alkyl group having 1 to 5 carbon atoms, a hydroxyl group, or an alkoxy group having 1 to 6 carbon atoms.
In formula (61), R 1f , R 2f and R 3f each independently represent a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an isopropyl group;
The methacrylic acid-containing composition of claim 1 , wherein R 4f is a hydroxy group.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A1 is 2000 or less.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A21 is 1,000 or less.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A3 is 2000 or less.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A4 is 1,000 or less.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A5 is 1,000 or less.
The methacrylic acid-containing composition according to claim 1, wherein the molecular weight of component A6 is 1,000 or less.
The methacrylic acid-containing composition according to claim 1, wherein component B is at least one selected from the group consisting of phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds.
The methacrylic acid-containing composition according to claim 1, wherein component B is at least one selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds.
The methacrylic acid-containing composition according to claim 1, wherein component B is a phenolic compound.
The methacrylic acid-containing composition according to claim 1, wherein component B is at least one selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenylphosphite, and phenothiazine.
The methacrylic acid-containing composition according to claim 1, wherein component B is at least one selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, and 2,6-di-t-butyl-4-methylphenol.
The methacrylic acid-containing composition according to claim 1, wherein the concentration of methacrylic acid is 98.50 to 99.99% by mass.
The methacrylic acid-containing composition according to claim 1, which does not contain diacetyl or contains diacetyl at a concentration of 55 μmol/L or less.
A method for producing a methacrylic acid ester, comprising esterifying the methacrylic acid of the methacrylic acid-containing composition according to any one of claims 1 to 51.
A polymerizable composition comprising the methacrylic acid-containing composition according to any one of claims 1 to 51.
The polymerizable composition according to claim 53, further comprising a monomer copolymerizable with methacrylic acid.
A method for producing a methacrylic acid polymer, comprising polymerizing a polymerizable composition containing the methacrylic acid-containing composition according to any one of claims 1 to 51.
The method of claim 55, wherein the polymerizable composition further contains a monomer copolymerizable with methacrylic acid.
The method according to claim 56, wherein the polymerizable composition contains 50 parts by mass or more of a monomer copolymerizable with methacrylic acid per 100 parts by mass of the polymerizable composition.